Light-emitting device, electronic device, and lighting device

ABSTRACT

A light-emitting device, an electronic device, or a lighting device with low power consumption and high reliability is provided. The light-emitting device includes a first light-emitting element, a second light-emitting element, a third light-emitting element, and a fourth light-emitting element. The first to fourth light-emitting elements include the same EL layer between an anode and a cathode. The EL layer includes a first light-emitting layer and a second light-emitting layer. The first light-emitting layer contains a fluorescent substance. The peak wavelength of an emission spectrum of the fluorescent substance in a toluene solution of the fluorescent substance is 440 nm to 460 nm, preferably 440 nm to 455 nm. The second light-emitting layer contains a phosphorescent substance. The first light-emitting element exhibits blue emission. The second light-emitting element exhibits green emission. The third light-emitting element exhibits red emission. The fourth light-emitting element exhibits yellow emission.

TECHNICAL FIELD

The present invention relates to an object, a method, or a manufacturingmethod. In addition, the present invention relates to a process, amachine, manufacture, or a composition of matter. In particular, oneembodiment of the present invention relates to a light-emitting element,a light-emitting device, an electronic device, a lighting device, adriving method thereof, or a manufacturing method thereof.

BACKGROUND ART

A light-emitting element using an organic compound as a luminous body,which has features such as thinness, lightness, high-speed response, andDC drive at low voltage, is expected to be applied to a next-generationflat panel display. In particular, a light-emitting device in whichlight-emitting elements are arranged in matrix is considered to haveadvantages in a wide viewing angle and excellent visibility over aconventional liquid crystal display device.

The light emission mechanism of a light-emitting element is said to beas follows: when a voltage is applied between a pair of electrodes withan EL layer including a luminous body provided therebetween, electronsinjected from the cathode and holes injected from the anode recombine inthe light emission center of the EL layer to form molecular excitons,and energy is released and light is emitted when the molecular excitonsreturn to the ground state. Singlet excitation and triplet excitationare known as excited states, and it is thought that light emission canbe achieved through either of the excited states.

In order to improve the characteristics of a light-emitting deviceincluding such light-emitting elements, improvement of an elementstructure, development of materials, and the like have been activelycarried out (for example, see Patent Document 1).

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2010-182699

DISCLOSURE OF INVENTION

In development of a light-emitting element, a reduction in drivingvoltage or a reduction in current amount is one of key factors inachieving lower consumption of products. In addition to elementstructures in which a carrier balance in an EL layer of a light-emittingelement can be controlled or the recombination probability of carrierscan be improved, the emission characteristics of a light-emitting layerin the EL layer are important factors for a reduction in the drivingvoltage or a reduction in the current amount of the light-emittingelement. Therefore, it is important to reduce the driving voltage orcurrent amount of the light-emitting element with the improved emissioncharacteristics of the light-emitting layer by using the EL layer havinga desired structure. The light-emitting element preferably has highreliability in addition to lower driving voltage.

In view of this, one embodiment of the present invention provides alight-emitting device, an electronic device, or a lighting device withlow power consumption. Another embodiment of the present inventionprovides a light-emitting device, an electronic device, or a lightingdevice with low power consumption and high reliability. Anotherembodiment of the present invention provides a novel light-emittingelement and a novel light-emitting device. Note that the descriptions ofthese objects do not disturb the existence of other objects. In oneembodiment of the present invention, there is no need to achieve all theobjects. Other objects will be apparent from and can be derived from thedescription of the specification, the drawings, the claims, and thelike.

One embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, a third light-emitting element, and a fourth light-emittingelement. The first light-emitting element includes a first EL layer, asecond EL layer, and a charge-generation layer. The secondlight-emitting element includes the first EL layer, the second EL layer,and the charge-generation layer. The third light-emitting elementincludes the first EL layer, the second EL layer, and thecharge-generation layer. The fourth light-emitting element includes thefirst EL layer, the second EL layer, and the charge-generation layer.The first EL layer includes a region functioning as part of the firstlight-emitting element, a region functioning as part of the secondlight-emitting element, a region functioning as part of the thirdlight-emitting element, and a region functioning as part of the fourthlight-emitting element. The second EL layer includes a regionfunctioning as part of the first light-emitting element, a regionfunctioning as part of the second light-emitting element, a regionfunctioning as part of the third light-emitting element, and a regionfunctioning as part of the fourth light-emitting element. Thecharge-generation layer includes a region functioning as part of thefirst light-emitting element, a region functioning as part of the secondlight-emitting element, a region functioning as part of the thirdlight-emitting element, and a region functioning as part of the fourthlight-emitting element. The charge-generation layer is between the firstEL layer and the second EL layer. The first EL layer contains an organiccompound in which each of two benzo[b]naphtho[1,2-d]furanylamineskeletons is independently bonded to a pyrene skeleton. The second ELlayer has a function of emitting phosphorescence. The firstlight-emitting element has a function of emitting blue light. The secondlight-emitting element has a function of emitting green light. The thirdlight-emitting element has a function of emitting red light.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, a third light-emitting element, and a fourth light-emittingelement. The first light-emitting element includes a first EL layer, asecond EL layer, and a charge-generation layer. The secondlight-emitting element includes the first EL layer, the second EL layer,and the charge-generation layer. The third light-emitting elementincludes the first EL layer, the second EL layer, and thecharge-generation layer. The fourth light-emitting element includes thefirst EL layer, the second EL layer, and the charge-generation layer.The first light-emitting element includes an anode. The first EL layeris between the anode and the charge-generation layer. The first EL layerincludes a region functioning as part of the first light-emittingelement, a region functioning as part of the second light-emittingelement, a region functioning as part of the third light-emittingelement, and a region functioning as part of the fourth light-emittingelement. The second EL layer includes a region functioning as part ofthe first light-emitting element, a region functioning as part of thesecond light-emitting element, a region functioning as part of the thirdlight-emitting element, and a region functioning as part of the fourthlight-emitting element. The charge-generation layer includes a regionfunctioning as part of the first light-emitting element, a regionfunctioning as part of the second light-emitting element, a regionfunctioning as part of the third light-emitting element, and a regionfunctioning as part of the fourth light-emitting element. Thecharge-generation layer is between the first EL layer and the second ELlayer. The first EL layer contains an organic compound in which each oftwo benzo[b]naphtho[1,2-d]furanylamine skeletons is independently bondedto a pyrene skeleton. The second EL layer has a function of emittingphosphorescence. The first light-emitting element has a function ofemitting blue light. The second light-emitting element has a function ofemitting green light. The third light-emitting element has a function ofemitting red light.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, a third light-emitting element, and a fourth light-emittingelement. The first light-emitting element includes a first EL layer, asecond EL layer, and a charge-generation layer. The secondlight-emitting element includes the first EL layer, the second EL layer,and the charge-generation layer. The third light-emitting elementincludes the first EL layer, the second EL layer, and thecharge-generation layer. The fourth light-emitting element includes thefirst EL layer, the second EL layer, and the charge-generation layer.The first light-emitting element includes an anode. The first EL layeris between the anode and the charge-generation layer. The first EL layerincludes a region functioning as part of the first light-emittingelement, a region functioning as part of the second light-emittingelement, a region functioning as part of the third light-emittingelement, and a region functioning as part of the fourth light-emittingelement. The second EL layer includes a region functioning as part ofthe first light-emitting element, a region functioning as part of thesecond light-emitting element, a region functioning as part of the thirdlight-emitting element, and a region functioning as part of the fourthlight-emitting element. The charge-generation layer includes a regionfunctioning as part of the first light-emitting element, a regionfunctioning as part of the second light-emitting element, a regionfunctioning as part of the third light-emitting element, and a regionfunctioning as part of the fourth light-emitting element. Thecharge-generation layer is between the first EL layer and the second ELlayer. The first EL layer contains an organic compound in which each oftwo benzo[b]naphtho[1,2-d]furanylamine skeletons is independently bondedto a pyrene skeleton. The second EL layer has a function of emittingyellow phosphorescence. The first light-emitting element has a functionof emitting blue light. The second light-emitting element has a functionof emitting green light. The third light-emitting element has a functionof emitting red light.

In the light-emitting device with any of the above structures, the twobenzo[b]naphtho[1,2-d]furanylamine skeletons are respectively bonded tothe 1-position and the 6-position of the pyrene skeleton.

In the light-emitting device with any of the above structures, each ofnitrogen atoms in the two benzo[b]naphtho[1,2-d]furanylamine skeletonsis independently bonded to the 6-position or the 8-position of abenzo[b]naphtho[1,2-d]furanyl group.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, a third light-emitting element, and a fourth light-emittingelement. The first light-emitting element includes a first EL layer, asecond EL layer, and a charge-generation layer. The secondlight-emitting element includes the first EL layer, the second EL layer,and the charge-generation layer. The third light-emitting elementincludes the first EL layer, the second EL layer, and thecharge-generation layer. The fourth light-emitting element includes thefirst EL layer, the second EL layer, and the charge-generation layer.The first light-emitting element includes an anode. The first EL layeris between the anode and the charge-generation layer. The first EL layerincludes a region functioning as part of the first light-emittingelement, a region functioning as part of the second light-emittingelement, a region functioning as part of the third light-emittingelement, and a region functioning as part of the fourth light-emittingelement. The second EL layer includes a region functioning as part ofthe first light-emitting element, a region functioning as part of thesecond light-emitting element, a region functioning as part of the thirdlight-emitting element, and a region functioning as part of the fourthlight-emitting element. The charge-generation layer includes a regionfunctioning as part of the first light-emitting element, a regionfunctioning as part of the second light-emitting element, a regionfunctioning as part of the third light-emitting element, and a regionfunctioning as part of the fourth light-emitting element. Thecharge-generation layer is between the first EL layer and the second ELlayer. The first EL layer contains a first organic compound representedby General Formula (G1) and a second organic compound. The second ELlayer has a function of emitting yellow phosphorescence. The firstlight-emitting element has a function of emitting blue light. The secondlight-emitting element has a function of emitting green light. The thirdlight-emitting element has a function of emitting red light.

In General Formula (G1), each of Ar¹ and Ar² independently represents asubstituted or unsubstituted aryl group having 6 to 13 carbon atomsforming a ring, and each of R¹ to R⁸, R¹⁰ to R¹⁸, and R²⁰ to R²⁸independently represents hydrogen, a substituted or unsubstituted alkylgroup having 1 to 6 carbon atoms, a substituted or unsubstituted alkoxygroup having 1 to 6 carbon atoms, a cyano group, halogen, a substitutedor unsubstituted haloalkyl group having 1 to 6 carbon atoms, or asubstituted or unsubstituted aryl group having 6 to 10 carbon atoms.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, a third light-emitting element, and a fourth light-emittingelement. The first light-emitting element includes a first EL layer, asecond EL layer, and a charge-generation layer. The secondlight-emitting element includes the first EL layer, the second EL layer,and the charge-generation layer. The third light-emitting elementincludes the first EL layer, the second EL layer, and thecharge-generation layer. The fourth light-emitting element includes thefirst EL layer, the second EL layer, and the charge-generation layer.The first light-emitting element includes an anode. The first EL layeris between the anode and the charge-generation layer. The first EL layerincludes a region functioning as part of the first light-emittingelement, a region functioning as part of the second light-emittingelement, a region functioning as part of the third light-emittingelement, and a region functioning as part of the fourth light-emittingelement. The second EL layer includes a region functioning as part ofthe first light-emitting element, a region functioning as part of thesecond light-emitting element, a region functioning as part of the thirdlight-emitting element, and a region functioning as part of the fourthlight-emitting element. The charge-generation layer includes a regionfunctioning as part of the first light-emitting element, a regionfunctioning as part of the second light-emitting element, a regionfunctioning as part of the third light-emitting element, and a regionfunctioning as part of the fourth light-emitting element. Thecharge-generation layer is between the first EL layer and the second ELlayer. The first EL layer contains a first organic compound representedby General Formula (G2) and a second organic compound. The second ELlayer has a function of emitting yellow phosphorescence. The firstlight-emitting element has a function of emitting blue light. The secondlight-emitting element has a function of emitting green light. The thirdlight-emitting element has a function of emitting red light.

In General Formula (G2), each of R¹ to R⁸ and R²⁹ to R³⁸ independentlyrepresents hydrogen, a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, a substituted or unsubstituted alkoxy group having 1to 6 carbon atoms, a cyano group, halogen, a substituted orunsubstituted haloalkyl group having 1 to 6 carbon atoms, or asubstituted or unsubstituted aryl group having 6 to 10 carbon atoms.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, a third light-emitting element, and a fourth light-emittingelement. The first light-emitting element includes a first EL layer, asecond EL layer, and a charge-generation layer. The secondlight-emitting element includes the first EL layer, the second EL layer,and the charge-generation layer. The third light-emitting elementincludes the first EL layer, the second EL layer, and thecharge-generation layer. The fourth light-emitting element includes thefirst EL layer, the second EL layer, and the charge-generation layer.The first light-emitting element includes an anode. The first EL layeris between the anode and the charge-generation layer. The first EL layerincludes a region functioning as part of the first light-emittingelement, a region functioning as part of the second light-emittingelement, a region functioning as part of the third light-emittingelement, and a region functioning as part of the fourth light-emittingelement. The second EL layer includes a region functioning as part ofthe first light-emitting element, a region functioning as part of thesecond light-emitting element, a region functioning as part of the thirdlight-emitting element, and a region functioning as part of the fourthlight-emitting element. The charge-generation layer includes a regionfunctioning as part of the first light-emitting element, a regionfunctioning as part of the second light-emitting element, a regionfunctioning as part of the third light-emitting element, and a regionfunctioning as part of the fourth light-emitting element. Thecharge-generation layer is between the first EL layer and the second ELlayer. The first EL layer contains a first organic compound representedby Structural Formula (132) and a second organic compound. The second ELlayer has a function of emitting yellow phosphorescence. The firstlight-emitting element has a function of emitting blue light. The secondlight-emitting element has a function of emitting green light. The thirdlight-emitting element has a function of emitting red light.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, a third light-emitting element, and a fourth light-emittingelement. The first light-emitting element, the second light-emittingelement, the third light-emitting element, and the fourth light-emittingelement include the same EL layer between an anode and a cathode. The ELlayer includes a first light-emitting layer and a second light-emittinglayer. The first light-emitting layer contains a fluorescent substance.The peak wavelength of an emission spectrum of the fluorescent substancein a toluene solution of the fluorescent substance is 440 nm to 460 nm,preferably 440 nm to 455 nm. The second light-emitting layer contains aphosphorescent substance. The first light-emitting element exhibits blueemission. The second light-emitting element exhibits green emission. Thethird light-emitting element exhibits red emission. The fourthlight-emitting element exhibits yellow emission.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, a third light-emitting element, and a fourth light-emittingelement. The first light-emitting element, the second light-emittingelement, the third light-emitting element, and the fourth light-emittingelement include, between an anode and a cathode, the same first EL layerand the same second EL layer between which the same charge-generationlayer is. The first EL layer includes a first light-emitting layer. Thesecond EL layer includes a second light-emitting layer. The firstlight-emitting layer contains a fluorescent substance. The peakwavelength of an emission spectrum of the fluorescent substance in atoluene solution of the fluorescent substance is 440 nm to 460 nm,preferably 440 nm to 455 nm. The second light-emitting layer contains aphosphorescent substance. The first light-emitting element exhibits blueemission. The second light-emitting element exhibits green emission. Thethird light-emitting element exhibits red emission. The fourthlight-emitting element exhibits yellow emission.

Another embodiment of the present invention is the light-emitting devicein which the half-width of the emission spectrum is greater than orequal to 20 nm and less than or equal to 50 nm.

Another embodiment of the present invention is the light-emitting devicein which the first light-emitting element has an x-coordinate greaterthan or equal to 0.13 and less than or equal to 0.17 and a y-coordinategreater than or equal to 0.03 and less than or equal to 0.08 on the xychromaticity diagram. Preferably, the first light-emitting element has ay-coordinate greater than or equal to 0.03 and less than or equal to0.07 on the xy chromaticity diagram.

Another embodiment of the present invention is the light-emitting devicein which light emission from the first light-emitting element is emittedto the outside of the light-emitting device through a blue color filter.

Another embodiment of the present invention is the light-emitting devicein which the power consumption of the light-emitting device except thepower consumption of a driving FET (the sum of power consumptions of thefirst to fourth light-emitting elements) is higher than or equal to 1mW/cm² and lower than or equal to 7 mW/cm² when light having anx-coordinate of 0.313 and a y-coordinate of 0.329 on the xy chromaticitydiagram is obtained with a luminance of 300 cd/m².

Another embodiment of the present invention is the light-emitting devicein which the power consumption (power consumption calculated from theproduct of current consumption and a voltage between an anode and acathode) of the light-emitting device including the power consumption ofthe driving FET is higher than or equal to 2 mW/cm² and lower than orequal to 15 mW/cm² in the case where light having an x-coordinate of0.313 and a y-coordinate of 0.329 on the xy chromaticity diagram isobtained with a luminance of 300 cd/m².

Another embodiment of the present invention is an electronic deviceincluding the light-emitting device, and a connection terminal or anoperation key.

One embodiment of the present invention includes, in its category, inaddition to a light-emitting device including a light-emitting element,an electronic device including the light-emitting element or thelight-emitting device (specifically, an electronic device including thelight-emitting element or the light-emitting device and a connectionterminal or an operation key) and a lighting device including thelight-emitting element or the light-emitting device (specifically, alighting device including the light-emitting element or thelight-emitting device and a housing). The light-emitting device in thisspecification therefore refers to an image display device or a lightsource (e.g., a lighting device). In addition, the light-emitting deviceincludes, in its category, a module in which a light-emitting device isconnected to a connector such as a flexible printed circuit (FPC) or atape carrier package (TCP), a module in which a printed wiring board isprovided on the tip of a TCP, and a module in which an integratedcircuit (IC) is directly mounted on a light-emitting element by a chipon glass (COG) method.

According to one embodiment of the present invention, a novellight-emitting device, a novel electronic device, and a novel lightingdevice can each be provided. Furthermore, a light-emitting device, anelectronic device, and a lighting device with low power consumption caneach be provided. Furthermore, a light-emitting device, an electronicdevice, and a lighting device with low power consumption and highreliability can each be provided. Note that the description of theseeffects does not disturb the existence of other effects. One embodimentof the present invention does not necessarily achieve all the effectslisted above. Other effects will be apparent from and can be derivedfrom the description of the specification, the drawings, the claims, andthe like.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B each illustrate a light-emitting element.

FIG. 2 shows a light emission mechanism of a light-emitting element.

FIG. 3 shows a light emission mechanism of a light-emitting element.

FIG. 4 shows a light emission mechanism of a light-emitting element.

FIG. 5 illustrates a light-emitting device.

FIGS. 6A and 6B illustrate a light-emitting device.

FIGS. 7A, 7B, 7C, 7D, 7D′-1, and 7D′-2 illustrate electronic devices.

FIGS. 8A to 8C illustrate an electronic device.

FIG. 9 illustrates lighting devices.

FIG. 10 illustrates a light-emitting device.

FIGS. 11A and 11B illustrate an example of a touch panel of anembodiment.

FIGS. 12A and 12B illustrate an example of a touch panel of anembodiment.

FIGS. 13A and 13B illustrate an example of a touch panel of anembodiment.

FIGS. 14A and 14B are a block diagram and a timing chart of a touchsensor.

FIG. 15 is a circuit diagram of a touch sensor.

FIG. 16 shows luminance-current density characteristics ofLight-emitting Elements 1 to 3.

FIG. 17 shows current efficiency-luminance characteristics ofLight-emitting Elements 1 to 3.

FIG. 18 shows luminance-voltage characteristics of Light-emittingElements 1 to 3.

FIG. 19 shows current-voltage characteristics of Light-emitting Elements1 to 3.

FIG. 20 shows chromaticity coordinates of Light-emitting Elements 1 to3.

FIG. 21 shows luminance-current density characteristics of ComparativeLight-emitting Elements 1 to 3.

FIG. 22 shows current efficiency-luminance characteristics ofComparative Light-emitting Elements 1 to 3.

FIG. 23 shows luminance-voltage characteristics of ComparativeLight-emitting Elements 1 to 3.

FIG. 24 shows current-voltage characteristics of ComparativeLight-emitting Elements 1 to 3.

FIG. 25 shows chromaticity coordinates of Comparative Light-emittingElements 1 to 3.

FIG. 26 shows an emission spectrum of 1,6BnfAPrn-03 in a toluenesolution of 1,6BnfAPrn-03.

FIG. 27 illustrates a structure of a light-emitting element.

FIG. 28 shows luminance-current density characteristics ofLight-emitting Elements 4 to 7.

FIG. 29 shows current efficiency-luminance characteristics ofLight-emitting Elements 4 to 7.

FIG. 30 shows luminance-voltage characteristics of Light-emittingElements 4 to 7.

FIG. 31 shows current-voltage characteristics of Light-emitting Elements4 to 7.

FIG. 32 shows chromaticity coordinates of Light-emitting Elements 4 to7.

FIG. 33 shows luminance-current density characteristics of ComparativeLight-emitting Elements 4 to 6.

FIG. 34 shows current efficiency-luminance characteristics ofComparative Light-emitting Elements 4 to 6.

FIG. 35 shows luminance-voltage characteristics of ComparativeLight-emitting Elements 4 to 6.

FIG. 36 shows current-voltage characteristics of ComparativeLight-emitting Elements 4 to 6.

FIG. 37 shows a light-emitting device of an example.

FIG. 38 shows a comparison of power consumption.

FIG. 39 shows luminance-current density characteristics ofLight-emitting Elements 8 and 9.

FIG. 40 shows current efficiency-luminance characteristics ofLight-emitting Elements 8 and 9.

FIG. 41 shows luminance-voltage characteristics of Light-emittingElements 8 and 9.

FIG. 42 shows current-voltage characteristics of Light-emitting Elements8 and 9.

FIG. 43 shows emission spectra of Light-emitting Elements 8 and 9.

FIG. 44 shows normalized luminance-time dependence characteristics ofLight-emitting Elements 8 and 9.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below in detailwith reference to the drawings. Note that the present invention is notlimited to the following description, and various changes andmodifications can be made without departing from the spirit and scope ofthe present invention. Therefore, the present invention should not beconstrued as being limited to the description in the followingembodiments.

Note that the terms “film” and “layer” can be interchanged with eachother depending on the case or circumstances. For example, in somecases, the term “conductive film” can be used instead of the term“conductive layer,” and the term “insulating layer” can be used insteadof the term “insulating film.”

Embodiment 1

In a light-emitting device of one embodiment of the present invention, alight-emitting element in which an EL layer including a light-emittinglayer is provided between a pair of electrodes is used. For thelight-emitting element, various structures can be employed; for example,a structure in which one EL layer is provided between a pair ofelectrodes (single structure) or a structure in which a plurality of ELlayers are stacked with a charge-generation layer therebetween (tandemstructure) can be employed. As one example of an element structure ofthe light-emitting element, a light-emitting element with a tandemstructure including two EL layers will be described below with referenceto FIG. 1A.

The light-emitting element illustrated in FIG. 1A has a structure inwhich two EL layers (103 a and 103 b) each including a light-emittinglayer are provided between a pair of electrodes (a first electrode 101and a second electrode 102). In the EL layer 103 a, a hole-injectionlayer 104 a, a hole-transport layer 105 a, a light-emitting layer 106 a,an electron-transport layer 107 a, an electron-injection layer 108 a,and the like are sequentially stacked over the first electrode 101. Inthe EL layer 103 b, a hole-injection layer 104 b, a hole-transport layer105 b, a light-emitting layer 106 b, an electron-transport layer 107 b,an electron-injection layer 108 b, and the like are sequentially stackedover the first electrode 101. A charge-generation layer 109 is providedbetween the EL layer 103 a and the EL layer 103 b.

The light-emitting layers (106 a and 106 b) each contain a plurality ofsubstances such as light-emitting substances in appropriate combination,and can emit fluorescent light or phosphorescent light of a desiredemission color. Note that a light-emitting layer containing a differentlight-emitting substance from the light-emitting layer 106 a or 106 bmay be further provided on the light-emitting layer 106 a or 106 b.

The charge-generation layer 109 has a function of injecting electronsinto one of the EL layers (103 a or 103 b) and injecting holes into theother of the EL layers (103 b or 103 a) when a voltage is appliedbetween the first electrode 101 and the second electrode 102. Thus, inFIG. 1A, when a voltage is applied such that the potential of the firstelectrode 101 is higher than that of the second electrode 102, thecharge-generation layer 109 injects electrons into the EL layer 103 aand injects holes into the EL layer 103 b.

Note that in terms of light extraction efficiency, the charge-generationlayer 109 preferably has a light-transmitting property with respect tovisible light (specifically, the charge-generation layer 109 has avisible light transmittance of 40% or more). The charge-generation layer109 functions even if it has lower conductivity than the first electrode101 or the second electrode 102.

In the light-emitting element illustrated in FIG. 1A, light emitted inall directions from the light-emitting layers (106 a and 106 b) includedin the EL layers (103 a and 103 b) can be resonated by the firstelectrode (reflective electrode) 101 and the second electrode(semi-transmissive and semi-reflective electrode) 102 which function asa micro optical resonator (microcavity). Light is emitted through thesecond electrode 102. The first electrode 101 is a reflective electrode,which has a stacked structure of a reflective conductive material and atransparent conductive material. Optical adjustment thereof is performedby controlling the thickness of the transparent conductive film. Theoptical adjustment may be performed by controlling the thickness of thehole-injection layer 104 a included in the EL layer 103 a.

As described above, the optical adjustment is performed by controllingthe thickness of the first electrode 101 or the hole-injection layer 104a, whereby spectra of a plurality of rays of monochromatic lightobtained from the light-emitting layers (106 a and 106 b) can benarrower, and light emission with high color purity can be obtained.

In the light-emitting element illustrated in FIG. 1A, the optical pathlength between the second electrode 102 functioning as asemi-transmissive and semi-reflective electrode and a light-emittingregion in the EL layer 103 b which is the nearest to the secondelectrode 102 is preferably smaller than λ/4 where λ is the wavelengthof light emitted from the light-emitting region. Here, thelight-emitting region means a region where holes and electrons arerecombined. With such a structure, light of standard white color can beobtained by a combination of a plurality of rays of monochromatic lightfrom the light-emitting layers (106 a and 106 b) of the light-emittingelement illustrated in FIG. 1A. The light-emitting layers (106 a and 106b) emit, for example, blue light (e.g., with an emission spectrum peakin the range of 400 nm to 480 nm, preferably in the range of 450 nm to470 nm), green light (e.g., with an emission spectrum peak in the rangeof 500 nm to 560 nm, preferably in the range of 520 nm to 555 nm), redlight (e.g., with an emission spectrum peak in the range of 580 nm to680 nm, preferably in the range of 600 nm to 620 nm), orange light(e.g., with an emission spectrum in the range of 580 nm to 610 nm,preferably in the range of 600 nm to 610 nm), or yellow light (e.g.,with an emission spectrum peak in the range of 555 nm to 590 nm,preferably in the range of 570 nm to 580 nm). Further, as specificcombinations of the emission colors of the light-emitting layers 106 aand 106 b (106 a/106 b), the following can be given: blue/green,blue/yellow, blue/red, green/blue, green/yellow, green/red, red/blue,red/green, and red/yellow.

Next, a specific example in manufacturing the above light-emittingelement will be described.

The first electrode 101 is a reflective electrode and thus is formedusing a conductive material having reflectivity, and a film whosevisible light reflectivity is greater than or equal to 40% and less thanor equal to 100%, preferably greater than or equal to 70% and less thanor equal to 100%, and resistivity is 1×10⁻² Ωcm or lower is used. Thesecond electrode 102 is formed using a conductive material havingreflectivity and a conductive material having a light-transmittingproperty, and a film whose visible light reflectivity is greater than orequal to 20% and less than or equal to 80%, preferably greater than orequal to 40% and less than or equal to 70%, and whose resistivity is1×10⁻² Ωcm or lower is used.

The optical path length between the first electrode 101 and the secondelectrode 102 is adjusted for each light having a desired wavelength sothat light having a desired wavelength from the light-emitting layers(106 a and 106 b) is resonated and can be intensified. Specifically, thethickness of the transparent conductive film used for part of the firstelectrode 101 is changed so that the distance between the electrodes ismλ/2 (m is a natural number) where λ is the desired wavelength of light.

Further, the optical path lengths between the first electrode 101 andthe light-emitting layers (106 a and 106 b) emitting light having adesired wavelength are adjusted in order to intensify the light having adesired wavelength. Specifically, the thickness of the transparentconductive film that can be used for part of the first electrode 101 orthe thickness of an organic film forming the hole-injection layer 104 ais changed so that the optical path length is (2m′+1)λ/4 (m′ is anatural number) where λ is the desired wavelength of light.

In that case, the optical path length between the first electrode 101and the second electrode 102 is, to be exact, represented by the totalthickness from a reflective region in the first electrode 101 to areflective region in the second electrode 102. However, it is difficultto exactly determine the reflective regions in the first electrode 101and the second electrode 102; thus, it is assumed that the above effectcan be sufficiently obtained wherever the reflective regions may be setin the first electrode 101 and the second electrode 102. Further, theoptical path length between the first electrode 101 and thelight-emitting layer emitting desired light is, to be exact, the opticallength between the reflective region in the first electrode 101 and thelight-emitting region in the light-emitting layer emitting desiredlight. However, it is difficult to exactly determine the reflectiveregion in the first electrode 101 and the light-emitting region in thelight-emitting layer emitting desired light; thus, it is assumed thatthe above effect can be sufficiently obtained wherever the reflectiveregion and the light-emitting region may be set in the first electrode101 and the light-emitting layer emitting desired light.

For the first electrode 101 and the second electrode 102, any of metals,alloys, electrically conductive compounds, mixtures thereof, and thelike can be used as appropriate. Specific examples are indium oxide-tinoxide (indium tin oxide), indium oxide-tin oxide containing silicon orsilicon oxide, indium oxide-zinc oxide (indium zinc oxide), indium oxidecontaining tungsten oxide and zinc oxide, gold (Au), platinum (Pt),nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe),cobalt (Co), copper (Cu), palladium (Pd), and titanium (Ti). Inaddition, an element belonging to Group 1 or Group 2 of the periodictable, for example, an alkali metal such as lithium (Li) or cesium (Cs),an alkaline earth metal such as calcium (Ca) or strontium (Sr),magnesium (Mg), an alloy containing such an element (MgAg, AlLi), a rareearth metal such as europium (Eu) or ytterbium (Yb), an alloy containingsuch an element, graphene, and the like can be used. The first electrode101 and the second electrode 102 can be formed by, for example, asputtering method or an evaporation method (including a vacuumevaporation method).

The hole-injection layers (104 a and 104 b) inject holes into thelight-emitting layers (106 a and 106 b) through the hole-transportlayers (105 a and 105 b) having a high hole-transport property, and canbe formed using an acceptor material such as molybdenum oxide, vanadiumoxide, ruthenium oxide, tungsten oxide, or manganese oxide.Alternatively, the hole-injection layers (104 a and 104 b) can be formedusing a phthalocyanine-based compound such as phthalocyanine(abbreviation: H₂Pc) or copper phthalocyanine (abbreviation: CuPc), anaromatic amine compound such as4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB) orN,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD), a compound containing an electron-withdrawinggroup (halogen or a cyano group) such as7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, or2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN), or an organic acceptor material such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)(abbreviation: PEDOT/PSS).

The hole-injection layers (104 a and 104 b) may contain a hole-transportmaterial and an acceptor substance. When the hole-injection layers (104a and 104 b) contain a hole-transport material and an acceptorsubstance, electrons are extracted from the hole-transport material bythe acceptor substance to generate holes and the holes are injected intothe light-emitting layers (106 a and 106 b) through the hole-transportlayers (105 a and 105 b). The hole-transport layers (105 a and 105 b)are formed using a hole-transport material.

Specific examples of the hole-transport material, which is used for thehole-injection layers (104 a and 104 b) and the hole-transport layers(105 a and 105 b), include aromatic amine compounds such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N′-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), and4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB);3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2); and3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1). Other examples include carbazole derivativessuch as 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA).The substances listed here are mainly ones that have a hole mobility of10⁻⁶ cm²/Vs or higher. Note that any substance other than the substanceslisted here may be used as long as the hole-transport property is higherthan the electron-transport property.

Other examples include high molecular compounds such aspoly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine)(abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), andpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD).

Examples of the acceptor substance used for the hole-injection layers(105 a and 105 b) include the above acceptor material and an organicacceptor material. Among them, an oxide of a metal belonging to any ofGroups 4 to 8 of the periodic table is preferably used; in particular,molybdenum oxide is preferably used.

The light-emitting layers (106 a and 106 b) each contain alight-emitting substance. The light-emitting layers (106 a and 106 b)each contain an electron-transport material that is an organic compoundand/or a hole-transport material in addition to the light-emittingsubstance; in the light-emitting element of one embodiment of thepresent invention, one of the light-emitting layers (106 a and 106 b)contains a fluorescent substance whose emission spectrum in a toluenesolution of the fluorescent substance has a peak wavelength of 440 nm to460 nm, preferably 440 nm to 455 nm or an organic compound in which twobenzo[b]naphtho[1,2-d]furanylamine skeletons are bonded to a pyreneskeleton. The emission spectrum of the fluorescent substance preferablyhas a half-width greater than or equal to 20 nm and less than or equalto 50 nm.

As the fluorescent substance whose emission spectrum in a toluenesolution has a peak wavelength of 440 nm to 460 nm, for example, asubstance having an aromatic diamine skeleton is preferably used. Morepreferably, a substance having a pyrenediamine skeleton is used. As thesubstance having a pyrenediamine skeleton, to be more specific, anorganic compound in which two benzo[b]naphtho[1,2-d]furanylamineskeletons are bonded to a pyrene skeleton and which is represented byGeneral Formula (G1) below is preferably used. Note that the fluorescentsubstance that can be used in this embodiment is not limited to thefollowing example.

As the organic compound in which two benzo[b]naphtho[1,2-d]furanylamineskeletons are bonded to a pyrene skeleton, an organic compoundrepresented by General Formula (G1) below can be used. Note that theorganic compound represented by General Formula (G1) below exhibits bluefluorescence.

In General Formula (G1), each of Ar¹ and Ar² independently represents asubstituted or unsubstituted aryl group having 6 to 13 carbon atomsforming a ring; and each of R¹ to R⁸, R¹⁰ to R¹⁸, and R²⁰ to R²⁸independently represents hydrogen, a substituted or unsubstituted alkylgroup having 1 to 6 carbon atoms, a substituted or unsubstituted alkoxygroup having 1 to 6 carbon atoms, a cyano group, halogen, a substitutedor unsubstituted haloalkyl group having 1 to 6 carbon atoms, or asubstituted or unsubstituted aryl group having 6 to 10 carbon atoms.

For specific examples of the organic compound represented by GeneralFormula (G1), Embodiment 2 can be referred to.

There is no particular limitation on a material that can be used as alight-emitting substance for the other of the light-emitting layers (106a and 106 b), and a light-emitting material which converts singletexcitation energy into light emission in a visible light region or alight-emitting material which converts triplet excitation energy intolight emission in a visible light region can be used.

As an example of the light-emitting material which converts singletexcitation energy into light emission in a visible light region, asubstance emitting fluorescence can be given. Examples of the substanceemitting fluorescence include a pyrene derivative, an anthracenederivative, a triphenylene derivative, a fluorene derivative, acarbazole derivative, a dibenzothiophene derivative, a dibenzofuranderivative, a dibenzoquinoxaline derivative, a quinoxaline derivative, apyridine derivative, a pyrimidine derivative, a phenanthrene derivative,and a naphthalene derivative. A pyrene derivative is particularlypreferable because it has a high emission quantum yield. Specificexamples of the pyrene derivative includeN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(1,6mMemFLPAPrn),N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N′-diphenylpyrene-1,6-diamine(1,6FLPAPrn),N,N′-bis(dibenzofuran-2-yl)-N,N′-diphenylpyrene-1,6-diamine (1,6FrAPrn),and N,N′-bis(dibenzothiophen-2-yl)-N,N′-diphenylpyrene-1,6-diamine(1,6ThAPrn).

Examples of the light-emitting material which converts tripletexcitation energy into light emission in a visible light region includea substance emitting phosphorescence and a thermally activated delayedfluorescence (TADF) material. Note that the TADF material is a materialthat can up-convert a triplet excited state into a singlet excited state(i.e., reverse intersystem crossing is possible) using a little thermalenergy and efficiently exhibits light emission (fluorescence) from thesinglet excited state. The TADF is efficiently obtained under thecondition where the difference in energy between the triplet excitedlevel and the singlet excited level is greater than or equal to 0 eV andless than or equal to 0.2 eV, preferably greater than or equal to 0 eVand less than or equal to 0.1 eV. Note that “delayed fluorescence”exhibited by the TADF material refers to light emission having the samespectrum as nominal fluorescence and an extremely long lifetime. Thelifetime is 10⁻⁶ seconds or longer, preferably 10⁻³ seconds or longer.

As the substance emitting phosphorescence, an iridium-, rhodium-, orplatinum-based organometallic complex or metal complex can be used; inparticular, an organoiridium complex such as an iridium-basedortho-metalated complex is preferable. As an ortho-metalated ligand, a4H-triazole ligand, a 1H-triazole ligand, an imidazole ligand, apyridine ligand, a pyrimidine ligand, a pyrazine ligand, an isoquinolineligand, and the like can be given. As the metal complex, a platinumcomplex having a porphyrin ligand and the like can be given. Examples ofthe substance emitting phosphorescence includebis[2-(3′,5′bistrifluoromethylphenyl)pyridinato-N,C^(2′)]iridium(III)picolinate(abbreviation: Ir(CF₃ppy)₂(pic)),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: Flracac),tris(2-phenylpyridinato)iridium(III) (abbreviation: Ir(ppy)₃),bis(2-phenylpyridinato)iridium(III) acetylacetonate (abbreviation:Ir(ppy)₂(acac)), tris(acetylacetonato)(monophenanthroline)terbium(III)(abbreviation: Tb(acac)₃(Phen)), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: Ir(bzq)₂(acac)),bis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(dpo)₂(acac)),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C^(2′)}iridium(III)acetylacetonate (abbreviation: Ir(p-PF-ph)₂(acac)),bis(2-phenylbenzothiazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(bt)₂(acac)),bis[2-(2′-benzo[4,5-a]thienyl)pyridinato-N,C^(3′)]iridium(III)acetylacetonate (abbreviation: Ir(btp)₂(acac)),bis(1-phenylisoquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(piq)₂(acac)),(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium (III)(abbreviation: Ir(Fdpq)₂(acac)),(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]),(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]),(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: Ir(tppr)₂(acac))bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)₂(dpm)])(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]),2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: PtOEP), tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: Eu(DBM)₃(Phen)), andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: Eu(TTA)₃(Phen)).

Specific examples of the TADF material include fullerene, a derivativethereof, an acridine derivative such as proflavine, and eosin. Otherexamples include a metal-containing porphyrin, such as a porphyrincontaining magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum(Pt), indium (In), or palladium (Pd). Examples of the metal-containingporphyrin include a protoporphyrin-tin fluoride complex (SnF₂(ProtoIX)), a mesoporphyrin-tin fluoride complex (SnF₂(Meso IX)), ahematoporphyrin-tin fluoride complex (SnF₂(Hemato IX)), a coproporphyrintetramethyl ester-tin fluoride complex (SnF₂(Copro III-4Me)), anoctaethylporphyrin-tin fluoride complex (SnF₂(OEP)), anetioporphyrin-tin fluoride complex (SnF₂(Etio I)), and anoctaethylporphyrin-platinum chloride complex (PtCl₂OEP). Alternatively,a heterocyclic compound including a 7 c-electron rich heteroaromaticring and a π-electron deficient heteroaromatic ring can be used, such as2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(PIC-TRZ). Note that a material in which the π-electron richheteroaromatic ring is directly bonded to the π-electron deficientheteroaromatic ring is particularly preferable because both the donorproperty of the π-electron rich heteroaromatic ring and the acceptorproperty of the π-electron deficient heteroaromatic ring are increasedand the energy difference between the S₁ level and the T₁ level becomessmall.

As a material that can be used as the light-emitting substance for theother of the light-emitting layers (106 a and 106 b), a light-emittingmaterial which converts triplet excitation energy into light emission ina visible light region is preferably used. More preferably, aphosphorescent substance which exhibits yellow phosphorescence is used.With such a structure, a light-emitting element with low powerconsumption can be obtained. With the use of such a light-emittingelement as a display element of a light-emitting device, powerconsumption for obtaining white emission can be effectively reduced.

In the case where an electron-transport material is used as the organiccompound for the light-emitting layers (106 a and 106 b), a π-electrondeficient heteroaromatic compound such as a nitrogen-containingheteroaromatic compound is preferable, examples of which includequinoxaline derivatives and dibenzoquinoxaline derivatives such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 2CzPDBq-III),7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), and6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:6mDBTPDBq-II).

In the case where a hole-transport material is used as the organiccompound for the light-emitting layers (106 a and 106 b), a π-electronrich heteroaromatic compound (e.g., a carbazole derivative or an indolederivative) or an aromatic amine compound is preferable, examples ofwhich include 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBA1BP),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1),4,4′,4″-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation:1′-TNATA),2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9′-bifluorene(abbreviation: DPA2SF),N,N′-bis(9-phenylcarbazol-3-yl)-N,N′-diphenylbenzene-1,3-diamine(abbreviation: PCA2B),N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine(abbreviation: DPNF),N,N′,N″-triphenyl-N,N′,N″-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine(abbreviation: PCA3B),2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: PCASF),2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: DPASF),N,N′-bis[4-(carbazol-9-yl)phenyl]-N,N′-diphenyl-9,9-dimethylfluorene-2,7-diamine(abbreviation: YGA2F),4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation: TPD),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N′-phenyl-N′-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine(abbreviation: DFLADFL),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA1),3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA2),4,4′-bis(N-{4-[N-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl(abbreviation: DNTPD),3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole(abbreviation: PCzTPN2), and3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2).

In the case where the light-emitting substance used for thelight-emitting layer is a substance emitting phosphorescence, examplesof the organic compound used for the light-emitting layer include anaromatic amine and a carbazole derivative in addition to a zinc- oraluminum-based metal complex, an oxadiazole derivative, a triazolederivative, a benzimidazole derivative, a quinoxaline derivative, adibenzoquinoxaline derivative, a dibenzothiophene derivative, adibenzofuran derivative, a pyrimidine derivative, a triazine derivative,a pyridine derivative, a bipyridine derivative, and a phenanthrolinederivative.

In the case where the light-emitting substance used for thelight-emitting layer is a substance emitting fluorescence, an anthracenederivative or a tetracene derivative whose S₁ level is high and T₁ levelis low is preferably used. Specific examples include9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (PCzPA),9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (CzPA),7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (cgDBCzPA),6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan(2mBnfPPA),9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene(FLPPA), 5,12-diphenyltetracene, and 5,12-bis(biphenyl-2-yl)tetracene.

The electron-transport layers (107 a and 107 b) are layers containing asubstance with a high electron-transport property. For theelectron-transport layers (107 a and 107 b), a metal complex such asAlq₃, tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),BAlq, Zn(BOX)₂, or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc(II)(abbreviation: Zn(BTZ)₂) can be used. Moreover, a heteroaromaticcompound such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-tert-biphenylyl)-4-phenyl-5-(4-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), or4-4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can beused, as well. Further alternatively, it is possible to use a highmolecular compound such as poly(2,5-pyridinediyl) (abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py) orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy). The substances mentioned here are mainly onesthat have an electron mobility of 1×10⁻⁶ cm²/Vs or higher. However, anysubstance other than the above substances may also be used for theelectron-transport layers (107 a and 107 b) as long as theelectron-transport property is higher than the hole-transport property.

Each of the electron-transport layers (107 a and 107 b) is not limitedto a single layer, and may be a stack including two or more layerscontaining any of the above substances.

The electron-injection layers (108 a and 108 b) are layers containing asubstance with a high electron-injection property. For theelectron-injection layers (108 a and 108 b), an alkali metal, analkaline earth metal, or a compound thereof such as lithium fluoride(LiF), cesium fluoride (CsF), calcium fluoride (CaF₂), or lithium oxide(LiO_(x)) can be used. A rare earth metal compound like erbium fluoride(ErF₃) can also be used. An electride may also be used for theelectron-injection layers (108 a and 108 b). Examples of the electrideinclude a substance in which electrons are added at high concentrationto calcium oxide-aluminum oxide. Any of the substances for forming theelectron-transport layers (107 a and 107 b), which are listed above, canalso be used.

The electron-injection layers (108 a and 108 b) each may be formed usinga composite material in which an organic compound and an electron donorare mixed. The composite material is superior in an electron-injectionproperty and an electron-transport property, since electrons aregenerated in the organic compound by the electron donor. In this case,the organic compound is preferably a material that is excellent intransporting the generated electrons. Specifically, for example, thesubstances for forming the electron-transport layers (107 a and 107 b)(e.g., a metal complex or a heteroaromatic compound), which are givenabove, can be used. As the electron donor, a substance showing anelectron-donating property with respect to the organic compound may beused. Specifically, an alkali metal, an alkaline earth metal, and a rareearth metal are preferable, and lithium, cesium, magnesium, calcium,erbium, ytterbium, and the like are given. In addition, an alkali metaloxide or an alkaline earth metal oxide is preferable, and lithium oxide,calcium oxide, and barium oxide are given. A Lewis base such asmagnesium oxide can also be used. An organic compound such astetrathiafulvalene (abbreviation: TTF) can also be used.

In the light-emitting element described in this embodiment, the opticalpath length between the second electrode 102 and the light-emittingregion in the EL layer 103 b which is the nearest to the secondelectrode 102 is preferably smaller than λ/4 where λ is the wavelengthof light emitted from the light-emitting region. For that reason, thetotal thickness of the electron-transport layer (107 b) and theelectron-injection layer (108 b) is preferably adjusted as appropriateso that the optical path length between the second electrode 102 and thelight-emitting region in the EL layer 103 b which is the nearest to thesecond electrode 102 can be smaller than λ/4.

The charge-generation layer 109 may have either a structure in which anelectron acceptor (acceptor) is added to a hole-transport material or astructure in which an electron donor (donor) is added to anelectron-transport material. Alternatively, both of these structures maybe stacked.

In the case of the structure in which an electron acceptor is added to ahole-transport material, as the hole-transport material, for example, anaromatic amine compound such as NPB, TPD, TDATA, MTDATA, or4,4′-bis[N-(Spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB) can be used. The substances listed here are mainlyones that have a hole mobility of 10⁻⁶ cm²/Vs or higher. Note that anysubstance other than the above substances may be used as long as thehole-transport property is higher than the electron-transport property.

Examples of the electron acceptor include7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and HAT-CN. Oxides of metals belonging to Groups 4to 8 of the periodic table can also be used. Specifically, vanadiumoxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide,tungsten oxide, manganese oxide, and rhenium oxide are preferablebecause of their high electron-accepting properties. Among these,molybdenum oxide is especially preferable because it is stable in theair, has a low hygroscopic property, and is easy to handle.

On the other hand, in the case of the structure in which an electrondonor is added to an electron-transport material, as theelectron-transport material, for example, a metal complex having aquinoline skeleton or a benzoquinoline skeleton, such as Alq, Almq₃,BeBq₂, or BAlq can be used. Alternatively, a metal complex having anoxazole-based ligand or a thiazole-based ligand, such as Zn(BOX)₂ orZn(BTZ)₂ can be used. Further alternatively, in addition to such a metalcomplex, PBD, OXD-7, TAZ, BPhen, BCP, or the like can be used. Thesubstances listed here are mainly ones that have an electron mobility of10⁻⁶ cm²/Vs or higher. Note that any substance other than the substanceslisted here may be used as long as the electron-transport property ishigher than the hole-transport property.

As the electron donor, it is possible to use an alkali metal, analkaline earth metal, a rare earth metal, a metal belonging to Group 2or 13 of the periodic table, or an oxide or carbonate thereof.Specifically, lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca),ytterbium (Yb), indium (In), lithium oxide, cesium carbonate, or thelike is preferably used. Alternatively, an organic compound such astetrathianaphthacene may be used as the electron donor.

Note that by the formation of the charge-generation layer 109 using anyof the above materials, it is possible to suppress an increase indriving voltage caused by stacking the EL layers.

Note that each of the hole-injection layers (104 a and 104 b), thehole-transport layers (105 a and 105 b), the light-emitting layers (106a and 106 b), the electron-transport layers (107 a and 107 b), theelectron-injection layers (108 a and 108 b), and the charge-generationlayer 109 can be formed by a method such as an evaporation method (e.g.,a vacuum evaporation method), an ink-jet method, or a coating method.

Although the light-emitting element having two EL layers is described inthis embodiment, a light-emitting element in which three or more ELlayers are stacked can also be used.

Note that a light-emitting element of the present invention may have asingle structure of one EL layer as illustrated in FIG. 1B. In thiscase, the light-emitting layer 106 includes the first light-emittinglayer 106 a and the second light-emitting layer 106 b. For thestructures of the other components, the above description of the layersdenoted by the same reference numerals can be referred to.

In the case of the single structure, emission efficiency can be improvedwith a separate coloring structure illustrated in FIG. 27. Even whencoloring is performed only once, the emission efficiency of alight-emitting element with the structure illustrated in FIG. 27 can beequivalent to that of a light-emitting element in which light-emittinglayers are separately colored (in the case of blue and yellow, coloringis performed twice).

A substrate 1100, first electrodes (1102B, 1102G, 1102R, and 1102Y)provided over the substrate 1100, a second electrode 1104, a blackmatrix 1105, color filters (1106B, 1106G, 1106R, and 1106Y), and asealing substrate 1101 in the separate coloring structure are similar tothe components in FIGS. 1A and 1B. As for an EL layer, a hole-injectionlayer and hole-transport layer 1103 e, a yellow light-emitting layer1103 f, and an electron-transport layer and electron-injection layer1103 h can be used for all the light-emitting elements; only a bluelight-emitting layer 1103 d is separately colored and is provided in aportion where a blue light-emitting element is formed.

Here, in the yellow light-emitting layer 1103 f and the bluelight-emitting layer 1103 d, carrier balance is adjusted so that arecombination region can be formed on the electrode side which is closerto the light-emitting layer that is separately colored (in this case,the blue light-emitting layer). In FIG. 27, the blue light-emittinglayer 1103 d is separately colored and is closer to the first electrode(here, anode) than the yellow light-emitting layer is; thus, hostmaterials and light-emitting materials for the blue light-emitting layerand the yellow light-emitting layer are selected such that theelectron-transport property of each of the blue light-emitting layer andthe yellow light-emitting layer is higher than the hole-transportproperty thereof. With such a structure, only blue light emission can beobtained from the light-emitting element including the bluelight-emitting layer 1103 d, and only yellow light emission can beobtained from the other elements, and the emission efficiency can beequivalent to that of an element in which a blue light-emitting layerand a yellow light-emitting layer are separately colored.

The light emission mechanism of the above light-emitting element dependson the structure of the light-emitting layer, and will be describedbelow with reference to FIG. 2, FIG. 3, and FIG. 4.

(1) First, two kinds of light emission mechanisms in the case where thelight-emitting layer (106 a or 106 b) contains a light-emittingsubstance (a guest material 121) and a first organic compound (a hostmaterial 122) and the light-emitting substance (the guest material 121)is a substance that emits fluorescence will be described.

Note that in the light-emitting layer (106 a or 106 b), excited statesare formed by carrier recombination; the excited states are formedmostly as the excited states of the host material 122 because the hostmaterial 122 is present in larger amounts than the guest material 121.Here, the ratio of the singlet excited state to the triplet excitedstate formed by carrier recombination (hereinafter, exciton generationprobability) is approximately 1:3.

(i) When the T₁ level of the host material 122 is higher than the T₁level of the guest material 121

Energy is transferred from the host material 122 in the triplet excitedstate to the guest material 121 (triplet energy transfer); however,since the guest molecule is a fluorescent substance, its triplet excitedstate does not provide light emission. Further, since the guest moleculeis present in small amounts in the light-emitting layer, triplet-tripletannihilation (TTA) is unlikely to occur and thus the triplet excitedstate of the guest molecule is thermally deactivated. Therefore, atriplet exciton cannot be utilized for light emission; approximately 25%of injected carriers can be utilized for light emission at a maximum.

(ii) When the T₁ level of the host material 122 is lower than the T₁level of the guest material 121

The correlation of energy levels of the host material 122 and the guestmaterial 121 is shown in FIG. 2. The following explains what terms andsigns in FIG. 2 represent:

Guest: the guest material 121 (fluorescent material);

Host: the host material 122;

S_(FH): the level of the lowest singlet excited state of the hostmaterial 122;

T_(FH): the level of the lowest triplet excited state of the hostmaterial 122;

S_(FG): the level of the lowest singlet excited state of the guestmaterial 121 (fluorescent material); and

T_(FG): the level of the lowest triplet excited state of the guestmaterial 121 (fluorescent material).

In this case, the host molecule is present in large amounts in thelight-emitting layer, so that triplet-triplet annihilation (TTA) islikely to occur; thus, some of the triplet excitons in the host material122 are converted into the level of the lowest single excited state ofthe host material 122 (S_(FH)). Then, energy is transferred from thelevel of the lowest single excited state of the host material 122(S_(FH)) to the level of the lowest singlet excited state of the guestmaterial 121 (S_(FG)) (Route A). Consequently, the guest material 121emits light.

Since the T₁ level of the host material 122 (T_(FH)) is lower than theT₁ level of the guest material 121 (T_(FG)), even in the case wherecarriers are directly recombined in the guest material 121 and thetriplet exciton is generated, energy is transferred from the T₁ level(T_(FG)) to the T₁ level of the host material 122 (T_(FH)) (Route B) andcan be utilized for TTA. As a result, emission efficiency can beimproved compared with the above case (i).

(2) Next, a light emission mechanism in the case where thelight-emitting layer (106 a or 106 b) contains a light-emittingsubstance (a guest material 131), a first organic compound 132, and asecond organic compound 133 and the light-emitting substance (the guestmaterial 131) is a substance that emits phosphorescence will bedescribed. Note that the first organic compound 132 serves as a hostmaterial, and the weight proportion of the first organic compound 132 inthe light-emitting layer is larger than that of the second organiccompound 133 in the light-emitting layer.

In the light-emitting layer (106 a or 106 b), there is no particularlimitation on the combination of the first organic compound 132 and thesecond organic compound 133 as long as they can form an exciplex(excited complex) 134; however, it is preferable that one of them be amaterial having a hole-transport property and the other be a materialhaving an electron-transport property. In that case, a donor-acceptorexcited state is formed easily, which allows the exciplex 134 to beformed efficiently. In the case where the combination of the firstorganic compound 132 and the second organic compound 133 is acombination of the material having a hole-transport property and thematerial having an electron-transport property, the carrier balance canbe controlled easily by adjusting the mixing ratio. Specifically, theratio of the material having a hole-transport property to the materialhaving an electron-transport property is preferably 1:9 to 9:1 (weightratio). Since the carrier balance can be easily controlled with theabove-described structure, a recombination region can also be easilycontrolled.

The correlation of energy levels of the light-emitting substance (guestmaterial) 131, the first organic compound 132, and the second organiccompound 133 is shown in FIG. 3. The following explains what terms andsigns in FIG. 3 represent:

Guest: the guest material (phosphorescent material) 131;

First organic compound: the first organic compound 132;

Second organic compound: the second organic compound 133;

Exciplex: the exciplex (excited complex) 134;

S_(PH): the level of the lowest singlet excited state of the firstorganic compound 132:

T_(PH): the level of the lowest triplet excited state of the firstorganic compound 132;

T_(PG): the level of the lowest triplet excited state of the guestmaterial (phosphorescent material) 131;

S_(E): the level of the lowest singlet excited state of the exciplex134; and

T_(E): the level of the lowest triplet excited state of the exciplex134.

In this case, the first organic compound 132 and the second organiccompound 133 form the exciplex 134. The level of the lowest singletexcited state of the exciplex 134 (S_(E)) and the level of the lowesttriplet excited state of the exciplex 134 (T_(E)) come close to eachother (Route C).

Note that the exciplex 134 is in an excited state formed by two kinds ofsubstances, and is formed by either photoexitation or electricalexcitation. In the case of photoexcitation, the exciplex 134 is formedin such a manner that one molecule in an excited state of one substanceforms a pair with one molecule in a ground state of the other substance.In the case of electrical excitation, there are two patterns ofelementary processes in which the exciplex is formed. One of them is thesame as in the case of photoexitation. The other is as follows: acationic molecule (hole) of one substance comes close to an anionicmolecule (electron) of the other substance, and thus the exciplex 134 isformed. At the start of light emission, the latter elementary process isdominant, and thus the exciplex 134 can be formed without the two kindsof substances being in an excited state. Therefore, emission startvoltage can be lowered, and in addition, driving voltage can be reduced.

When the exciplex 134 is formed, energy is transferred from the level ofthe lowest singlet excited state of the exciplex 134 (S_(E)) and thelevel of the lowest triplet excited state of the exciplex 134 (T_(E)) tothe level of the lowest triplet excited state of the guest material(phosphorescent material) 131 (T_(PG)) (Route D); thus, the guestmaterial 131 emits light. Note that the process in which the exciplex134 is formed (Route C) and energy is transferred from the exciplex 134to the guest material (phosphorescent material) 131 (Route D) isreferred to as exciplex-triplet energy transfer (ExTET).

When the exciplex 134 returns to a ground state by losing energy, thetwo kinds of substances that have formed the exciplex 134 serve as theoriginal different substances.

Depending on the combination of the first organic compound and thesecond organic compound which form the exciplex, with the use of thefluorescent material as the guest material, the guest material(fluorescent material) can emit light by energy transfer from theexciplex to the guest material (fluorescent material). The fluorescentmaterial includes in its category a thermally activated delayedfluorescence material.

(3) Then, a light emission mechanism in the case where one of thelight-emitting layers (106 a and 106 b) has a stacked structure in whichfirst light-emitting layer with the light emission mechanism (TTA)described in (ii) in (1) above and a second light-emitting layer withthe light emission mechanism (ExTET) described in (2) above are incontact with each other will be described. The correlation of energylevels in this case is shown in FIG. 4. The following explains whatterms and signs in FIG. 4 represent:

First light-emitting layer (fluorescence) 113: a first light-emittinglayer 113;

Second light-emitting layer (phosphorescence) 114: a secondlight-emitting layer 114;

S_(FH): the level of the lowest singlet excited state of the hostmaterial 122;

T_(FH): the level of the lowest triplet excited state of the hostmaterial 122;

S_(FG): the level of the lowest singlet excited state of the guestmaterial (fluorescent material) 121;

T_(FG): the level of the lowest triplet excited state of the guestmaterial (fluorescent material) 121;

S_(PH): the level of the lowest singlet excited state of the firstorganic compound 132;

T_(PH): the level of the lowest triplet excited state of the firstorganic compound 132;

T_(PG): the level of the lowest triplet excited state of the guestmaterial (phosphorescent material) 131;

S_(E): the level of the lowest singlet excited state of the exciplex134; and

T_(B): the level of the lowest triplet excited state of the exciplex134.

Since the exciplex 134 formed in the second light-emitting layer 114 ispresent only in an excited state, exciton diffusion between theexciplexes 134 is unlikely to occur. Furthermore, since the excitedlevel (S_(E)) of the exciplex 134 is lower than both the singlet excitedlevel (S_(PH)) of the first organic compound 132 and the singlet excitedlevel of the second organic compound in the second light-emitting layer114, singlet excitation energy is not diffused from the exciplex 134 tothe first organic compound 132 and the second organic compound. At theinterface between the first light-emitting layer 113 and the secondlight-emitting layer 114, in the case where energy (in particular,triplet energy) is transferred from the exciplex 134 formed in thesecond light-emitting layer 114 (the level of the lowest singlet excitedstate of the exciplex (S_(E)) or the level of the lowest triplet excitedstate of the exciplex (T_(B))) to the excited level (S_(FH), T_(FH)) ofthe host material 122 in the first light-emitting layer 113, singletexcitation energy is converted into light emission through a normalroute and triplet excitation energy is partly converted into lightemission by TTA in the first light-emitting layer 113. As a result,energy loss can be reduced. Furthermore, exciton diffusion between theexciplexes does not occur, and thus the energy transfer from theexciplex to the first light-emitting layer 113 occurs only at theinterface.

That most excitons in the second light-emitting layer 114 are present ina state of exciplex and excitation diffusion between the exciplexes 134is unlikely to occur in the second light-emitting layer 114 means theemission efficiency of the second light-emitting layer 114 can be kepteven in the case where the T₁ level of the host material 122 in thefirst light-emitting layer 113 that is a fluorescent layer is lower thanthe T₁ levels of the first organic compound 132 and the second organiccompound 133 in the second light-emitting layer 114. That is, in thisstructure, with the use of, as the host material in the firstlight-emitting layer 113, a condensed aromatic compound such as ananthracene derivative which is electrochemically stable and highlyreliable but has a low triplet excited level, light emission can beefficiently obtained from the phosphorescent layer which is adjacent tothe first light-emitting layer 113. Therefore, that the T₁ level of thehost material 122 in the first light-emitting layer 113 is lower thanthe T₁ levels of the first organic compound 132 and the second organiccompound 133 in the second light-emitting layer 114 is one feature ofthis structure.

In the first light-emitting layer 113, it is preferable that the S₁level (not illustrated) of the host material 122 be higher than the S₁level of the guest material 121 and the T₁ level (T_(FH)) of the hostmaterial 122 be lower than the T₁ level (T_(FG)) of the guest material121. With such a structure, even in the case where energy transferoccurs from the level (T_(E)) of the lowest triplet excited state of theexciplex 134 formed in the second light-emitting layer 114 to the level(T_(FH)) of the lowest triplet excited state of the host material 122 inthe first light-emitting layer 113 at the interface between the firstlight-emitting layer 113 and the second light-emitting layer 114, theenergy can be partly converted into light emission in the firstlight-emitting layer 113 by TTA. As a result, energy loss can bereduced.

In the case where the above stacked structure of the light-emittinglayers is used, light emitted from the first light-emitting layer 113preferably has a peak on the shorter wavelength side than light emittedfrom the second light-emitting layer 114. The reason for this is asfollows. Since the luminance of a light-emitting element using aphosphorescent material emitting light with a short wavelength tends tobe degraded quickly, a light-emitting element with less degradation ofluminance can be provided with the use of a fluorescent materialemitting light with a shorter wavelength than light emitted from thesecond light-emitting layer 114.

In the case where the above stacked structure of the light-emittinglayers is used, a third layer may be formed between the firstlight-emitting layer 113 and the second light-emitting layer 114 so thatthe first light-emitting layer 113 and the second light-emitting layer114 are not in contact with each other. With such a structure, energytransfer (in particular, triplet energy transfer) from the excited stateof the first organic compound 132 or the guest material (phosphorescentmaterial) 131 formed in the second light-emitting layer 114 to the hostmaterial 122 or the guest material (fluorescent material) 121 in thefirst light-emitting layer 113 due to the Dexter mechanism can beprevented. Note that the third layer in such a structure may be formedwith a thickness of several nanometers.

The third layer may be formed using a single material (hole-transportmaterial or electron-transport material) or both a hole-transportmaterial and an electron-transport material. In the case of a singlematerial, a bipolar material may be used. The bipolar material hererefers to a material in which the ratio between the electron mobilityand the hole mobility is 100 or less. The third layer can be formedusing the same material as the first light-emitting layer or the secondlight-emitting layer. Such a structure facilitates the fabrication ofthe light-emitting element and reduces the driving voltage.

The light-emitting element described in this embodiment preferably has amicrocavity structure. With this, light (monochromatic light rays) withdifferent wavelengths can be extracted even if the same EL layer isemployed. In comparison with a separate coloring structure (for example,R, G, and B are separately colored), the above structure is advantageousfor full color display owing to easiness in achieving higher resolutiondisplay or the like. Note that a combination with coloring layers (colorfilters) is also possible. With the microcavity structure, the intensityof light with a specific wavelength in the front direction can beincreased, whereby power consumption can be reduced. The above structureis particularly effective in the case of being used for a backlight or afront light in a color display (image display device) including pixelsof three or more colors but may also be used for a lighting device orthe like.

As a light-emitting device including the above light-emitting element, apassive matrix light-emitting device and an active matrix light-emittingdevice can be fabricated. Each of the light-emitting devices is oneembodiment of the present invention.

Note that there is no particular limitation on the structure of thetransistor (FET) in the case of fabricating the active matrixlight-emitting device. For example, a staggered FET or an invertedstaggered FET can be used as appropriate. A driver circuit formed overan FET substrate may be formed using both an n-type FET and a p-type FETor only either an n-type FET or a p-type FET. Furthermore, there is noparticular limitation on the crystallinity of a semiconductor film usedfor the FET. For example, either an amorphous semiconductor film or acrystalline semiconductor film may be used. Examples of a semiconductormaterial include Group 13 semiconductors (e.g., gallium), Group 14semiconductors (e.g., silicon), compound semiconductors (including oxidesemiconductors), and organic semiconductors.

Further, the light-emitting element described in this embodiment can beformed over a variety of substrates. There is no particular limitationon the type of substrate. Examples of the substrate include asemiconductor substrate (e.g., a single crystal substrate or a siliconsubstrate), an SOI substrate, a glass substrate, a quartz substrate, aplastic substrate, a metal substrate, a stainless steel substrate, asubstrate including stainless steel foil, a tungsten substrate, asubstrate including tungsten foil, a flexible substrate, an attachmentfilm, paper including a fibrous material, and a base material film.Examples of a glass substrate include a barium borosilicate glasssubstrate, an aluminoborosilicate glass substrate, and a soda lime glasssubstrate. Examples of a flexible substrate, an attachment film, and abase material film include plastics typified by polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), and polyethersulfone (PES); a synthetic resin of acrylic or the like; polypropylene;polyester; polyvinyl fluoride; polyvinyl chloride; polyamide; polyimide;aramid; epoxy; an inorganic vapor deposition film; and paper.

When a transistor is formed together with the light-emitting elementover any of these substrates, the use of a semiconductor substrate, asingle crystal substrate, an SOI substrate, or the like enables themanufacture of small-sized transistors with a small variation incharacteristics, size, shape, or the like and with high currentcapability. A circuit using such transistors achieves lower powerconsumption of the circuit or higher integration of the circuit.

When the above-described flexible substrate is used as a substrate overwhich a light-emitting element or a transistor is formed, thelight-emitting element or the transistor may be directly formed over theflexible substrate. Alternatively, part of or the entire light-emittingelement or transistor may be formed over a base substrate with aseparation layer provided therebetween and then the light-emittingelement or the transistor may be separated from the base substrate andtransferred to another substrate. When the light-emitting element or thetransistor is transferred to another substrate by using a separationlayer as described above, the light-emitting element or the transistorcan be formed over a substrate having low heat resistance or a flexiblesubstrate over which the light-emitting element or the transistor isdirectly formed with difficulty. Examples of the above separation layerinclude a stack including inorganic films, e.g., a tungsten film and asilicon oxide film, and an organic resin film of polyimide or the likeformed over a substrate. Examples of a substrate to which a transistoris transferred include, in addition to the above-described substratesover which a transistor can be formed, a paper substrate, a cellophanesubstrate, an aramid film substrate, a polyimide film substrate, a stonesubstrate, a wood substrate, a cloth substrate (including a naturalfiber (e.g., silk, cotton, or hemp), a synthetic fiber (e.g., nylon,polyurethane, or polyester), a regenerated fiber (e.g., acetate, cupra,rayon, or regenerated polyester), or the like), a leather substrate, anda rubber substrate. With the use of any of these substrates, an increasein durability or heat resistance and a reduction in weight or thicknesscan be achieved.

Note that the structure described in this embodiment can be used asappropriate in combination with any of the structures described in theother embodiments.

Embodiment 2

In this embodiment, an organic compound represented by General Formula(G1) will be described in detail.

In General Formula (G1), each of Ar¹ and Ar² independently represents asubstituted or unsubstituted aryl group having 6 to 13 carbon atomsforming a ring; and each of R¹ to R⁸, R¹⁰ to R¹⁸, and R²⁰ to R²⁸independently represents hydrogen, a substituted or unsubstituted alkylgroup having 1 to 6 carbon atoms, a substituted or unsubstituted alkoxygroup having 1 to 6 carbon atoms, a cyano group, halogen, a substitutedor unsubstituted haloalkyl group having 1 to 6 carbon atoms, or asubstituted or unsubstituted aryl group having 6 to 10 carbon atoms. Ina substance represented by General Formula (G1), each of R¹⁸ and R²⁸ ispreferably a substituted or unsubstituted phenyl group, in which casethe emission wavelength of the substance can be short. The substance inwhich R¹⁸ and R²⁸ are substituted or unsubstituted phenyl groups ispreferably used for a light-emitting element, in which case thelight-emitting element has an emission spectrum with a narrowhalf-width, high emission efficiency, and high reliability. In order toprevent distortion of a stereostructure, R¹⁸ and R²⁸ are furtherpreferably unsubstituted phenyl groups. In the case where R¹⁸ and R²⁸are each a phenyl group having a substituent, the substituent ispreferably an alkyl group having 1 to 6 carbon atoms or a phenyl group.

As the organic compound represented by General Formula (G1), an organiccompound represented by General Formula (G2) is preferably used becausean emission wavelength can be shorter.

In General Formula (G2), each of R¹ to R⁸ and R²⁹ to R³⁸ independentlyrepresents hydrogen, a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, a substituted or unsubstituted alkoxy group having 1to 6 carbon atoms, a cyano group, halogen, a substituted orunsubstituted haloalkyl group having 1 to 6 carbon atoms, or asubstituted or unsubstituted aryl group having 6 to 10 carbon atoms.

Specific examples of the substituted or unsubstituted aryl group having6 to 13 carbon atoms forming a ring in General Formula (G1) and thesubstituted or unsubstituted aryl group having 6 to 10 carbon atoms inGeneral Formula (G2) include a phenyl group, a 1-naphthyl group, a2-naphthyl group, an ortho-tolyl group, a meta-tolyl group, a para-tolylgroup, an ortho-biphenyl group, a meta-biphenyl group, a para-biphenylgroup, a 9,9-dimethyl-9H-fluoren-2-yl group, a9,9-diphenyl-9H-fluoren-2-yl group, a 9H-fluoren-2-yl group, apara-tert-butylphenyl group, and a mesityl group.

Specific examples of the substituted or unsubstituted alkyl groupshaving 1 to 6 carbon atoms in General Formulae (G1) and (G2) include amethyl group, an ethyl group, an n-propyl group, an isopropyl group, an-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group,an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentylgroup, a neopentyl group, an n-hexyl group, an isohexyl group, asec-hexyl group, a tert-hexyl group, a neo-hexyl group, a cyclohexylgroup, a 3-methylpentyl group, a 2-methylpentyl group, a 2-ethylbutylgroup, a 1,2-dimethylbutyl group, and a 2,3-dimethylbutyl group.

Specific examples of the substituted or unsubstituted alkoxy groupshaving 1 to 6 carbon atoms, the cyano group, the halogen, and thesubstituted or unsubstituted haloalkyl group having 1 to 6 carbon atomsin General Formulae (G1) and (G2) include a methoxy group, an ethoxygroup, an n-propoxy group, an isopropoxy group, an n-butoxy group, asec-butoxy group, an isobutoxy group, a tert-butoxy group, ann-pentyloxy group, an isopentyloxy group, a sec-pentyloxy group, atert-pentyloxy group, a neo-pentyloxy group, an n-hexyloxy group, anisohexyloxy group, a sec-hexyloxy group, a tert-hexyloxy group, aneo-hexyloxy group, a cyclohexyloxy group, a 3-methylpentyloxy group, a2-methylpentyloxy group, a 2-ethylbutoxy group, a 1,2-dimethylbutoxygroup, a 2,3-dimethylbutoxy group, a cyano group, fluorine, chlorine,bromine, iodine, and a trifluoromethyl group.

In the organic compound, benzonaphthofuranylamine is bonded to each ofthe 1-position and the 6-position of a pyrene skeleton, and each ofnitrogen atoms in benzonaphthofuranylamine is independently bonded tothe 6-position or the 8-position of a benzo[b]naphtho[1,2-d]furanylgroup. The structure in which benzonaphthofuranylamine is bonded to eachof the 1-position and the 6-position of the pyrene skeleton enables theeffective conjugation length from the pyrene skeleton tobenzonaphthofuranylamine to be increased. Consequently, the emissionpeak wavelength can be shifted to the long wavelength side in comparisonwith that in the case of monocyclic pyrene. Furthermore, with thisstructure, a molecular structure is stabilized by a benzonaphthofuranylgroup; thus, reliability is expected to be improved. Since the6-position or the 8-position of the benzo[b]naphtho[1,2-d]furanyl groupis bonded to an amine skeleton, the color purity of blue can be furtherincreased.

In the case where the 8-position of the benzo[b]naphtho[1,2-d]furanylgroup is bonded to the amine skeleton, light emission with a shorterwavelength can be obtained than in the case where the 6-position of thebenzo[b]naphtho[1,2-d]furanyl group is bonded to the amine skeleton.This is because the effective conjunction length is shorter in the casewhere the 8-position of the benzo[b]naphtho[1,2-d]furanyl group isbonded to the amine skeleton. When the 6-position of thebenzo[b]naphtho[1,2-d]furanyl group has an aryl group and the 8-positionof the benzo[b]naphtho[1,2-d]furanyl group is bonded to the amineskeleton, the color purity of blue can be increased by steric hindranceof the aryl group. Furthermore, intermolecular interaction can bereduced in this structure; thus, high color purity can be kept even whenthe concentration of the organic compound is high.

With the use of the above organic compound as a light-emitting substancein a light-emitting element of one embodiment of the present invention,driving voltage for obtaining desired luminance can be reduced.Furthermore, a highly reliable light-emitting element can be obtained.

Specific examples of the above organic compounds (General Formulae (G1)and (G2)) that can be used in a light-emitting element of one embodimentof the present invention are shown (Structural Formulae (100) to (133)).Note that the present invention is not limited thereto.

The above organic compound emits blue light with high color purity. Bluelight emission having the chromaticity coordinates defined by thenational television standards committee (NTSC), i.e., (x, y)=(0.14,0.08) or near that or light emission of blue deeper than that can beobtained. Therefore, with the use of such an organic compound for alight-emitting element, the driving voltage of the light-emittingelement can be low and the reliability thereof can be high. Furthermore,with the use of such a light-emitting element, the power consumption ofa light-emitting device, an electronic device, and a lighting device ofembodiments of the present invention can be reduced, and the lifetimethereof can be prolonged.

Note that the structure described in this embodiment can be used asappropriate in combination with any of the structures described in theother embodiments.

Embodiment 3

In this embodiment, one embodiment of a light-emitting device in whichthe light-emitting element described in Embodiment 1 is combined with acoloring layer (color filter or the like) will be described. In thisembodiment, the structure of a pixel portion of the light-emittingdevice will be described with reference to FIG. 5.

In FIG. 5, a plurality of FETs 502 is formed over a substrate 501. Eachof the FETs 502 is electrically connected to a light-emitting element(507R, 507G, 507B, or 507W). Specifically, each of the FETs 502 iselectrically connected to a first electrode 503 that is a pixelelectrode of the light-emitting element. A partition 504 is provided soas to cover edge portions of adjacent first electrodes 503.

Note that the first electrode 503 in this embodiment serves as areflective electrode. An EL layer 505 is formed over the first electrode503, and a second electrode 510 is formed over the EL layer 505. The ELlayer 505 includes a plurality of light-emitting layers each emittingmonochromatic light. The second electrode 510 serves as asemi-transmissive and semi-reflective electrode.

The light-emitting elements (507R, 507G, 507B, and 507W) emit light withdifferent colors. Specifically, the light-emitting element 507R isoptically adjusted to emit red light, and in a region indicated by 506R,red light is emitted through a coloring layer 508R in the directionindicated by an arrow. The light-emitting element 507G is opticallyadjusted to emit green light, and in a region indicated by 506G, greenlight is emitted through a coloring layer 508G in the directionindicated by an arrow. The light-emitting element 507B is opticallyadjusted to emit blue light, and in a region indicated by 506B, bluelight is emitted through a coloring layer 508B in the directionindicated by an arrow. The light-emitting element 507W is opticallyadjusted to emit white light, and in a region indicated by 506W, whitelight is emitted not through a coloring layer in the direction indicatedby an arrow.

As illustrated in FIG. 5, the coloring layers (508R, 508G, and 508B) areprovided on a transparent sealing substrate 511 that is provided abovethe substrate 501 over which the light-emitting elements (507R, 507G,507B, and 507W) are formed. The coloring layers (508R, 508G, and 508B)are provided so as to overlap with the respective light-emittingelements (507R, 507G, and 507B) which exhibit different emission colors.

A black layer (black matrix) 509 is provided to cover edge portions ofadjacent coloring layers (508R, 508G, and 508B). Note that the coloringlayers (508R, 508G, and 508B) and the black layer 509 may be coveredwith an overcoat layer that is formed using a transparent material.

The above light-emitting device has a structure in which light isextracted from the sealing substrate 511 side (a top emissionstructure), but may have a structure in which light is extracted fromthe substrate 501 side where the FETs are formed (a bottom emissionstructure). Note that in the light-emitting device having a top emissionstructure described in this embodiment, a light-shielding substrate or alight-transmitting substrate can be used as the substrate 501, whereasin a light-emitting device having a bottom emission structure, alight-transmitting substrate needs to be used as the substrate 501.

A structure illustrated in FIG. 10 can be employed as well as the abovestructure. The structure of the light-emitting elements (507R, 507G,507B, and 507Y) electrically connected to the FETs 502 over thesubstrate 501 in FIG. 10 is partly different from that in FIG. 5. Blueemission can be obtained with the use of the fluorescent substancedescribed in Embodiment 1 for the light-emitting layer 106 a in the ELlayer in Embodiment 1. Furthermore, yellow emission can be obtained fromthe light-emitting layer 106 b in the EL layer in Embodiment 1.

In this case, the light-emitting elements (507R, 507G, 507B, and 507Y)emit light of different colors. Specifically, the light-emitting element507R is optically adjusted to emit red light, and in a region indicatedby 506R, red light is emitted through the coloring layer 508R in thedirection indicated by an arrow. The light-emitting element 507G isoptically adjusted to emit green light, and in a region indicated by506G, green light is emitted through the coloring layer 508G in thedirection indicated by an arrow. The light-emitting element 507B isoptically adjusted to emit blue light, and in a region indicated by506B, blue light is emitted through the coloring layer 508B in thedirection indicated by an arrow. The light-emitting element 507Y isoptically adjusted to emit yellow light, and in a region indicated by506Y, yellow light is emitted through a coloring layer 508Y in thedirection indicated by an arrow.

As illustrated in FIG. 10, the coloring layers (508R, 508G, 508B, and508Y) are provided on the transparent sealing substrate 511 that isprovided above the substrate 501 over which the light-emitting elements(507R, 507G, 507B, and 507Y) are formed. The coloring layers (508R,508G, 508B, and 508Y) are provided so as to overlap with the respectivelight-emitting elements (507R, 507G, 507B, and 507Y) which exhibitdifferent emission colors.

In the light-emitting device of one embodiment of the present invention,blue light emitted from the light-emitting element 507B and extractedthrough the coloring layer 508B to the outside of the light-emittingdevice preferably has chromaticity coordinates of (x, y)=(greater thanor equal to 0.13 and less than or equal to 0.17, greater than or equalto 0.03 and less than or equal to 0.08) on the xy chromaticity diagramso that deep blue emission can be obtained. Preferably, blue lightemitted from the light-emitting element 507B and extracted through thecoloring layer 508B to the outside of the light-emitting device has ay-coordinate greater than or equal to 0.03 and less than or equal to0.07.

With the use of blue emission having such chromaticity, the luminance ofblue emission needed for obtaining white emission can be reduced. Sincethe amount of current consumed by the blue light-emitting element forobtaining predetermined white emission is sufficiently larger than thatconsumed by the light-emitting element of the other colors, an effect ofreducing the amount of current due to a reduction in the luminance ofblue emission needed for obtaining white emission is considerable.

Although current efficiency is generally decreased owing to desiredchromaticity of blue emission, the effect of reducing the luminance ofblue emission needed for obtaining white emission is considerable. As aresult, the amount of current flowing in the blue light-emitting elementfor obtaining predetermined white emission is significantly reduced, andaccordingly power consumption of the whole light-emitting device isreduced.

When the chromaticity of blue emission corresponds to deep blue asdescribed above, the color of emission obtained by synthesis of the blueemission and yellow emission changes and a third emission color neededfor obtaining predetermined white emission changes in some cases. Forexample, in the case where blue emission has the chromaticitycoordinates defined by NTSC, i.e., (x, y)=(0.14, 0.08) or near that andyellow emission has chromaticity coordinates of (x, y)=(0.45, 0.54) ornear that, a red emission component is further needed for obtainingwhite emission having chromaticity at approximately D65 in addition tolight emission obtained by synthesis of the blue emission and the yellowemission. On the other hand, in the case where blue emission has thechromaticity coordinates defined by NTSC or near that and yellowemission has chromaticity coordinates of (x, y)=(0.46, 0.53) orchromaticity coordinates of redder emission (that is, x is larger than0.46 and y is smaller than 0.53), white emission having chromaticity atapproximately D65 can be obtained by addition of a green emissioncomponent to light emission obtained by synthesis of the blue emissionand the yellow emission. However, in the case where yellow emission haschromaticity coordinates of redder emission (that is, x is larger than0.46 and y is smaller than 0.53), the current efficiency of yellowpixels is reduced owing to a reduction in luminosity factor. That is, aneffect of a reduction in power consumption is reduced accordingly.

In this manner, the third emission color needed for obtaining whiteemission having chromaticity at approximately D65 depends on the colorsof blue emission and yellow emission. The current efficiency of greenemission is generally higher than that of red emission, and thus isadvantageous. However, in the case where yellow emission haschromaticity coordinates of redder emission (that is, x is larger than0.46 and y is smaller than 0.53) as described above, the currentefficiency of yellow pixels is reduced owing to a reduction in theluminosity factor of yellow emission. An influence of a reduction in thecurrent efficiency of yellow emission with a high luminosity factor isconsiderable, and thus it is preferable that the chromaticity of yellowemission be not near the chromaticity of red emission.

In the case where deep blue emission having chromaticity coordinates of(x, y)=(greater than or equal to 0.13 and less than or equal to 0.17,greater than or equal to 0.03 and less than or equal to 0.08) is used,the chromaticity of yellow with a high luminosity factor is kept (thatis, the chromaticity which is not too near the chromaticity of redemission) and white emission having chromaticity at approximately D65can be obtained with the use of green emission as third emission inaddition to blue emission and yellow emission. With such a structure,the current efficiency can be kept high because yellow emission has ahigh luminosity factor. Furthermore, the luminance needed for greenemission in this structure is lower than that in the case where redemission is used as the third emission. Since the luminosity factor ofgreen emission is higher than that of red emission, and the currentefficiency of a green light-emitting element is generally higher thanthat of a red light-emitting element, the amount of current needed forobtaining the third emission is significantly reduced. As a result,driving voltage is reduced, and thus power consumption can be reduced.The chromaticity coordinates of the yellow emission at this time arepreferably (x, y)=(greater than or equal to 0.44 and less than or equalto 0.46, greater than or equal to 0.53 and less than or equal to 0.55).

Although the luminance components of the blue light-emitting element andthe light-emitting element that exhibits the third emission forobtaining the predetermined white emission are reduced, they can becompensated for by increasing the luminance of the yellow light-emittingelement. Since the luminosity factor of the yellow emission issignificantly high, the current efficiency of the yellow light-emittingelement is significantly high. An increase in power consumption due tothe increase in luminance needed for obtaining the yellow emission canbe compensated for by a reduction in power consumption due to areduction in the luminance needed for the blue light-emitting elementand the light-emitting element that exhibits the third emission. As aresult, a reduction in power consumption can be achieved.

In order that deep blue emission having chromaticity coordinates of (x,y)=(greater than or equal to 0.13 and less than or equal to 0.17,greater than or equal to 0.03 and less than or equal to 0.08),preferably (greater than or equal to 0.13 and less than or equal to0.17, greater than or equal to 0.03 and less than or equal to 0.07) onthe xy chromaticity diagram can be obtained, the peak wavelength of anemission spectrum of a fluorescent material contained in a firstlight-emitting element in a toluene solution of the fluorescent materialis set greater than or equal to 440 nm and less than or equal to 460 nm,preferably greater than or equal to 440 nm and less than or equal to 455nm. The chromaticity of the blue light-emitting element can be adjustedwith the use of a color filter or the like; however, only a small amountof light having the above wavelength is filtered out by a color filter,and light emission from the fluorescent material can be efficientlyutilized. Thus, the half-width of the emission spectrum of thefluorescent material in the toluene solution is preferably greater thanor equal to 20 nm and less than or equal to 50 nm.

With the use of blue emission having such chromaticity, powerconsumption for obtaining white emission having chromaticity coordinatesof (x, y)=(0.313, 0.329) on the xy chromaticity diagram at approximatelyD65 can be reduced. Specifically, in the case where white emissionhaving chromaticity coordinates of (x, y)=(0.313, 0.329) on the xychromaticity diagram is obtained with a luminance of 300 cd/m², thepower consumption of the light-emitting device except the powerconsumption of the driving FETs can be higher than or equal to 1 mW/cm²and lower than or equal to 7 mW/cm², and the power consumption of thelight-emitting device including the power consumption of the drivingFETs (the power consumption calculated from the product of currentconsumption and a voltage between an anode and a cathode) can be higherthan or equal to 2 mW/cm² and lower than or equal to 15 mW/cm².

With the above structure, light-emitting elements that exhibit aplurality of emission colors (red, blue, green, and yellow) can beprovided, and in addition, a light-emitting device that is capable ofemitting white light with high efficiency by combination of theseemission colors can be provided.

For the light-emitting device of one embodiment of the presentinvention, a variety of substrates can be used. There is no particularlimitation on the type of substrate. Examples of the substrate include asemiconductor substrate (e.g., a single crystal substrate or a siliconsubstrate), an SOI substrate, a glass substrate, a quartz substrate, aplastic substrate, a metal substrate, a stainless steel substrate, asubstrate including stainless steel foil, a tungsten substrate, asubstrate including tungsten foil, a flexible substrate, an attachmentfilm, paper including a fibrous material, and a base material filmExamples of a glass substrate include a barium borosilicate glasssubstrate, an aluminoborosilicate glass substrate, and a soda lime glasssubstrate. Examples of a flexible substrate, an attachment film, and abase material film include plastics typified by polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone(PES), and polytetrafluoroethylene (PTFE); acrylic; polypropylene;polyester; polyvinyl fluoride; polyvinyl chloride; polyamide; polyimide;aramid; epoxy; an inorganic vapor deposition film; and paper.

The use of a semiconductor substrate, a single crystal substrate, an SOIsubstrate, or the like for a transistor enables the manufacture ofsmall-sized transistors with a small variation in characteristics, size,shape, or the like and with high current capability. A circuit usingsuch transistors achieves lower power consumption of the circuit orhigher integration of the circuit.

A semiconductor device such as a transistor may be forming after aseparation layer is provided over the substrate. The separation layercan be used when part or the whole of a semiconductor device formed overthe separation layer is separated from the substrate and transferredonto another substrate. In such a case, the transistor can betransferred to a substrate having low heat resistance or a flexiblesubstrate as well. Examples of the above separation layer include astack including inorganic films, e.g., a tungsten film and a siliconoxide film, and an organic resin film of polyimide or the like formedover a substrate.

In other words, after the transistor or the light-emitting element isformed using one substrate, the transistor or the light-emitting elementmay be transferred to another substrate. Examples of a substrate towhich the transistor or the light-emitting element is transferredinclude, in addition to the above-described substrates over which atransistor can be formed, a paper substrate, a cellophane substrate, anaramid film substrate, a polyimide film substrate, a stone substrate, awood substrate, a cloth substrate (including a natural fiber (e.g.,silk, cotton, or hemp), a synthetic fiber (e.g., nylon, polyurethane, orpolyester), a regenerated fiber (e.g., acetate, cupra, rayon, orregenerated polyester), or the like), a leather substrate, and a rubbersubstrate. When such a substrate is used, a transistor with excellentproperties or low power consumption can be formed, a device with highdurability and high heat resistance can be provided, or a reduction inweight or thickness can be achieved. Note that in the case where aflexible light-emitting device is manufactured, a transistor or alight-emitting element may be directly formed over a flexible substrate.

Note that the structure described in this embodiment can be used asappropriate in combination with any of the structures described in theother embodiments.

Embodiment 4

In this embodiment, a light-emitting device including a light-emittingelement of one embodiment of the present invention will be described.

The light-emitting device may be either a passive matrix light-emittingdevice or an active matrix light-emitting device. Note that any of thelight-emitting elements described in the other embodiments can be usedfor the light-emitting device described in this embodiment.

In this embodiment, an active matrix light-emitting device will bedescribed with reference to FIGS. 6A and 6B.

Note that FIG. 6A is a top view illustrating a light-emitting device andFIG. 6B is a cross-sectional view taken along the chain line A-A′ inFIG. 6A. In the active matrix light-emitting device of this embodiment,a pixel portion 602, a driver circuit portion (a source line drivercircuit) 603, and driver circuit portions (gate line driver circuits)604 a and 604 b are provided over an element substrate 601. The pixelportion 602, the driver circuit portion 603, and the driver circuitportions 604 a and 604 b are sealed between the element substrate 601and a sealing substrate 606 with a sealant 605.

In addition, a lead wiring 607 for connecting an external input terminalis provided over the element substrate 601. Through the external inputterminal, a signal (e.g., a video signal, a clock signal, a startsignal, or a reset signal) or a potential is transmitted from theoutside to the driver circuit portion 603 and the driver circuitportions 604 a and 604 b. Here, a flexible printed circuit (FPC) 608 isprovided as an example of the external input terminal. Although only theFPC is illustrated here, the FPC may be provided with a printed wiringboard (PWB). The light-emitting device in this specification includes,in its category, not only the light-emitting device itself but also thelight-emitting device provided with the FPC or the PWB.

Next, a cross-sectional structure will be described with reference toFIG. 6B. The driver circuit portion and the pixel portion are formedover the element substrate 601; the driver circuit portion 603 that isthe source line driver circuit and the pixel portion 602 are illustratedhere.

As an example of the driver circuit portion 603, an FET 609 and an FET610 are combined. Note that the driver circuit portion 603 may be formedwith a circuit including transistors having the same conductivity type(either an n-channel transistor or a p-channel transistor) or a CMOScircuit including an n-channel transistor and a p-channel transistor. Inthis embodiment, the driver circuit is integrated with the substrate;however, the driver circuit is not necessarily formed over thesubstrate, and may be formed outside the substrate.

The pixel portion 602 includes a plurality of pixels each of whichincludes a switching FET 611, a current control FET 612, and a firstelectrode (anode) 613 that is electrically connected to a wiring (asource electrode or a drain electrode) of the current control FET 612.In this embodiment, the pixel portion 602 includes, but is not limitedto, two FETs, the switching FET 611 and the current control FET 612. Thepixel portion 602 may include, for example, three or more FETs and acapacitor in combination.

As the FETs 609, 610, 611, and 612, for example, a staggered transistoror an inverted staggered transistor can be used. Examples of asemiconductor material that can be used for the FETs 609, 610, 611, and612 include Group 13 semiconductors (e.g., gallium), Group 14semiconductors (e.g., silicon), compound semiconductors, oxidesemiconductors, and organic semiconductors. In addition, there is noparticular limitation on the crystallinity of the semiconductormaterial, and an amorphous semiconductor or a crystalline semiconductorcan be used. In particular, an oxide semiconductor is preferably usedfor the FETs 609, 610, 611, and 612. Examples of the oxide semiconductorinclude an In—Ga oxide and an In-M-Zn oxide (M is Al, Ga, Y, Zr, La, Ce,or Nd). For example, an oxide semiconductor that has an energy gap of 2eV or more, preferably 2.5 eV or more, further preferably 3 eV or moreis used for the FETs 609, 610, 611, and 612, so that the off-statecurrent of the transistors can be reduced.

An insulator 614 is formed to cover end portions of the first electrode613. In this embodiment, the insulator 614 is formed using a positivephotosensitive acrylic resin. The first electrode 613 is used as ananode in this embodiment.

The insulator 614 preferably has a curved surface with curvature at anupper end portion or a lower end portion thereof. This providesfavorable coverage with a film to be formed over the insulator 614. Theinsulator 614 can be formed using, for example, either a negativephotosensitive resin or a positive photosensitive resin. The material ofthe insulator 614 is not limited to an organic compound, and aninorganic compound such as silicon oxide, silicon oxynitride, or siliconnitride can also be used.

An EL layer 615 and a second electrode (cathode) 616 are formed over thefirst electrode (anode) 613. The EL layer 615 includes at least alight-emitting layer. In addition to the light-emitting layer, ahole-injection layer, a hole-transport layer, an electron-transportlayer, an electron-injection layer, a charge-generation layer, and thelike can be provided as appropriate in the EL layer 615.

A light-emitting element 617 is formed with a stack of the firstelectrode (anode) 613, the EL layer 615, and the second electrode(cathode) 616. For the first electrode (anode) 613, the EL layer 615,and the second electrode (cathode) 616, the materials described inEmbodiment 1 can be used. Although not illustrated, the second electrode(cathode) 616 is electrically connected to the FPC 608 which is anexternal input terminal.

Although the cross-sectional view of FIG. 6B illustrates only onelight-emitting element 617, a plurality of light-emitting elements arearranged in matrix in the pixel portion 602. Light-emitting elementswhich provide three kinds of light emission (R, G, and B) areselectively formed in the pixel portion 602, whereby a light-emittingdevice capable of full color display can be fabricated. Other than thelight-emitting element which provides three kinds of light emission (R,G, and B), for example, a light-emitting element that emits white (W),yellow (Y), magenta (M), and cyan (C) light may be formed. When theabove light-emitting element that provides several kinds of lightemission is provided as well as a light-emitting element that providesthree kinds of light emission (R, G, and B), for example, higher colorpurity, lower power consumption, or the like can be achieved.Alternatively, a light-emitting device capable of full color display maybe provided by a combination with color filters. The light-emittingdevice may have an improved emission efficiency and a reduced powerconsumption by combination with quantum dots.

Furthermore, the sealing substrate 606 is attached to the elementsubstrate 601 with the sealant 605, whereby a light-emitting element 617is provided in a space 618 surrounded by the element substrate 601, thesealing substrate 606, and the sealant 605. Note that the space 618 maybe filled with an inert gas (such as nitrogen or argon) or the sealant605.

An epoxy-based resin or glass frit is preferably used for the sealant605. The material preferably allows as little moisture and oxygen aspossible to penetrate. As the sealing substrate 606, a substrate formedusing any of the materials described in Embodiment 3, such as a glasssubstrate, a quartz substrate, or a plastic substrate formed offiber-reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester,acrylic, or the like, can be used. In the case where glass frit is usedas the sealant, the element substrate 601 and the sealing substrate 606are preferably glass substrates for high adhesion.

An active matrix light-emitting device can be obtained in the abovemanner.

Note that the structure described in this embodiment can be used asappropriate in combination with any of the structures described in theother embodiments.

Embodiment 5

In this embodiment, examples of a variety of electronic devices that aremanufactured using a light-emitting device which is one embodiment ofthe present invention will be described with reference to FIGS. 7A, 7B,7C, 7D, 7D′-1, and 7D′-2.

Examples of electronic devices including the light-emitting deviceinclude television devices (also referred to as TV or televisionreceivers), monitors for computers and the like, cameras such as digitalcameras and digital video cameras, digital photo frames, mobile phones(also referred to as cellular phones or portable telephone devices),portable game machines, portable information terminals, audio playbackdevices, and large game machines such as pachinko machines. Specificexamples of the electronic devices are illustrated in FIGS. 7A, 7B, 7C,7D, 7D′-1, and 7D′-2.

FIG. 7A illustrates an example of a television device. In the televisiondevice 7100, a display portion 7103 is incorporated in a housing 7101.The display portion 7103 can display images and may be a touch panel (aninput/output device) including a touch sensor (an input device). Notethat the light-emitting device which is one embodiment of the presentinvention can be used for the display portion 7103. In addition, here,the housing 7101 is supported by a stand 7105.

The television device 7100 can be operated by an operation switch of thehousing 7101 or a separate remote controller 7110. With operation keys7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the use of the receiver, general televisionbroadcasts can be received. Moreover, when the television device isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 7B illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnection port 7205, a pointing device 7206, and the like. Note thatthis computer can be manufactured using the light-emitting device whichis one embodiment of the present invention for the display portion 7203.The display portion 7203 may be a touch panel (an input/output device)including a touch sensor (an input device).

FIG. 7C illustrates a smart watch, which includes a housing 7302, adisplay panel 7304, operation buttons 7311 and 7312, a connectionterminal 7313, a band 7321, a clasp 7322, and the like.

The display panel 7304 mounted in the housing 7302 serving as a bezelincludes a non-rectangular display region. The display panel 7304 candisplay an icon 7305 indicating time, another icon 7306, and the like.The display panel 7304 may be a touch panel (an input/output device)including a touch sensor (an input device).

The smart watch illustrated in FIG. 7C can have a variety of functions,for example, a function of displaying a variety of information (e.g., astill image, a moving image, and a text image) on a display portion, atouch panel function, a function of displaying a calendar, date, time,and the like, a function of controlling processing with a variety ofsoftware (programs), a wireless communication function, a function ofbeing connected to a variety of computer networks with a wirelesscommunication function, a function of transmitting and receiving avariety of data with a wireless communication function, and a functionof reading program or data stored in a recording medium and displayingthe program or data on a display portion.

The housing 7302 can include a speaker, a sensor (a sensor having afunction of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, odor, or infrared rays), amicrophone, and the like. Note that the smart watch can be manufacturedusing the light-emitting device for the display panel 7304.

FIG. 7D illustrates an example of a mobile phone (e.g., smartphone). Amobile phone 7400 includes a housing 7401 provided with a displayportion 7402, a microphone 7406, a speaker 7405, a camera 7407, anexternal connection portion 7404, an operation button 7403, and thelike. In the case where a light-emitting device is manufactured byforming a light-emitting element of one embodiment of the presentinvention over a flexible substrate, the light-emitting element can beused for the display portion 7402 having a curved surface as illustratedin FIG. 7D.

When the display portion 7402 of the mobile phone 7400 illustrated inFIG. 7D is touched with a finger or the like, data can be input to themobile phone 7400. In addition, operations such as making a call andcreating an e-mail can be performed by touch on the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting data such as text. The thirdmode is a display-and-input mode in which two modes of the display modeand the input mode are combined.

For example, in the case of making a call or creating an e-mail, acharacter input mode mainly for inputting characters is selected for thedisplay portion 7402 so that characters displayed on the screen can beinput. In this case, it is preferable to display a keyboard or numberbuttons on almost the entire screen of the display portion 7402.

When a detection device such as a gyro sensor or an acceleration sensoris provided inside the mobile phone 7400, display on the screen of thedisplay portion 7402 can be automatically changed by determining theorientation of the mobile phone 7400 (whether the mobile phone is placedhorizontally or vertically).

The screen modes are changed by touch on the display portion 7402 oroperation with the button 7403 of the housing 7401. The screen modes canbe changed according to the kind of image displayed on the displayportion 7402. For example, when a signal for an image to be displayed onthe display portion is data of moving images, the screen mode is changedto the display mode. When the signal is text data, the screen mode ischanged to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed for a certain period while a signal detected by anoptical sensor in the display portion 7402 is detected, the screen modemay be controlled so as to be changed from the input mode to the displaymode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by touchon the display portion 7402 with the palm or the finger, wherebypersonal authentication can be performed. In addition, when a backlightor a sensing light source that emits near-infrared light is provided inthe display portion, an image of a finger vein, a palm vein, or the likecan be taken.

Furthermore, the light-emitting device can be used for a mobile phonehaving a structure illustrated in FIG. 7D′-1 or FIG. 7D′-2, which isanother structure of the mobile phone (e.g., smartphone).

Note that in the case of the structure illustrated in FIG. 7D′-1 or FIG.7D′-2, text data, image data, or the like can be displayed on secondscreens 7502(1) and 7502(2) of housings 7500(1) and 7500(2) as well asfirst screens 7501(1) and 7501(2). Such a structure enables a user toeasily see text data, image data, or the like displayed on the secondscreens 7502(1) and 7502(2) while the mobile phone is placed in user'sbreast pocket.

FIGS. 8A to 8C illustrate a foldable portable information terminal 9310.FIG. 8A illustrates the portable information terminal 9310 that isopened. FIG. 8B illustrates the portable information terminal 9310 thatis being opened or being folded. FIG. 8C illustrates the portableinformation terminal 9310 that is folded. The portable informationterminal 9310 is highly portable when folded. When the portableinformation terminal 9310 is opened, a seamless large display region ishighly browsable.

A display panel 9311 is supported by three housings 9315 joined togetherby hinges 9313. Note that the display panel 9311 may be a touch panel(an input/output device) including a touch sensor (an input device). Bybending the display panel 9311 at a connection portion between twohousings 9315 with the use of the hinges 9313, the portable informationterminal 9310 can be reversibly changed in shape from an opened state toa folded state. A light-emitting device of one embodiment of the presentinvention can be used for the display panel 9311. A display region 9312in the display panel 9311 is a display region that is positioned at aside surface of the portable information terminal 9310 that is folded.On the display region 9312, information icons, frequently-usedapplications, file shortcuts to programs, and the like can be displayed,and confirmation of information and start of application can be smoothlyperformed.

As described above, the electronic devices can be obtained byapplication of the light-emitting device which is one embodiment of thepresent invention. Note that the light-emitting device can be used forelectronic devices in a variety of fields without being limited to theelectronic devices described in this embodiment.

Embodiment 6

In this embodiment, examples of lighting devices will be described withreference to FIG. 9. Each of the lighting devices uses a light-emittingdevice which is one embodiment of the present invention.

FIG. 9 illustrates an example in which the light-emitting device is usedas an indoor lighting device 8001. Since the light-emitting device canhave a large area, it can be used for a lighting device having a largearea. In addition, with the use of a housing with a curved surface, alighting device 8002 which includes the housing, a cover, or a supportand in which a light-emitting region has a curved surface can also beobtained. A light-emitting element included in the light-emitting devicedescribed in this embodiment is in a thin film form, which allows thehousing to be designed more freely. Thus, the lighting device can beelaborately designed in a variety of ways. In addition, a wall of theroom may be provided with a large-sized lighting device 8003.

When the light-emitting device is used for a surface of a table, alighting device 8004 that has a function as a table can be obtained.When the light-emitting device is used as part of other furniture, alighting device that functions as the furniture can be obtained.

As described above, a variety of lighting devices that include thelight-emitting device can be obtained. Note that these lighting devicesare also embodiments of the present invention.

Note that the structure described in this embodiment can be used asappropriate in combination with any of the structures described in theother embodiments.

Embodiment 7

In this embodiment, a touch panel including a light-emitting element ofone embodiment of the present invention or a light-emitting device ofone embodiment of the present invention will be described with referenceto FIGS. 11A and 11B, FIGS. 12A and 12B, FIGS. 13A and 13B, FIGS. 14Aand 14B, and FIG. 15.

FIGS. 11A and 11B are perspective views of a touch panel 2000. Note thatFIGS. 11A and 11B illustrate typical components of the touch panel 2000for simplicity.

The touch panel 2000 includes a display portion 2501 and a touch sensor2595 (see FIG. 11B). Furthermore, the touch panel 2000 includes asubstrate 2510, a substrate 2570, and a substrate 2590. Note that thesubstrate 2510, the substrate 2570, and the substrate 2590 each haveflexibility.

The display portion 2501 includes a plurality of pixels over thesubstrate 2510, and a plurality of wirings 2511 through which signalsare supplied to the pixels. The plurality of wirings 2511 are led to aperipheral portion of the substrate 2510, and part of the plurality ofwirings 2511 forms a terminal 2519. The terminal 2519 is electricallyconnected to an FPC 2509(1).

The substrate 2590 includes the touch sensor 2595 and a plurality ofwirings 2598 electrically connected to the touch sensor 2595. Theplurality of wirings 2598 are led to a peripheral portion of thesubstrate 2590, and part of the plurality of wirings 2598 forms aconnection layer 2599. The connection layer 2599 is electricallyconnected to an FPC 2509(2). Note that in FIG. 11B, electrodes, wirings,and the like of the touch sensor 2595 provided on the back side of thesubstrate 2590 are indicated by solid lines for clarity.

As the touch sensor 2595, a capacitive touch sensor can be used, forexample. Examples of the capacitive touch sensor are a surfacecapacitive touch sensor and a projected capacitive touch sensor.

Examples of the projected capacitive touch sensor are a self capacitivetouch sensor and a mutual capacitive touch sensor, which differ mainlyin the driving method. The use of a mutual capacitive touch sensor ispreferable because multiple points can be sensed simultaneously.

First, an example of using a projected capacitive touch sensor will bedescribed below with reference to FIG. 11B. Note that in the case of aprojected capacitive touch sensor, a variety of sensors that can sensethe closeness or the contact of a sensing target such as a forger can beused.

The projected capacitive touch sensor 2595 includes electrodes 2591 andelectrodes 2592. The electrodes 2591 are electrically connected to anyof the plurality of wirings 2598, and the electrodes 2592 areelectrically connected to any of the other wirings 2598. The electrodes2592 each have a shape of a plurality of quadrangles arranged in onedirection with one corner of a quadrangle connected to one corner ofanother quadrangle with a wiring 2594 in one direction as illustrated inFIGS. 11A and 11B. In the same manner, the electrodes 2591 each have ashape of a plurality of quadrangles arranged in one direction with onecorner of a quadrangle connected to one corner of another quadrangle;however, the direction in which the electrodes 2591 are connected is adirection crossing the direction in which the electrodes 2592 areconnected. Note that the direction in which the electrodes 2591 areconnected and the direction in which the electrodes 2592 are connectedare not necessarily perpendicular to each other, and the electrodes 2591may be arranged to intersect with the electrodes 2592 at an anglegreater than 0° and less than 90°.

The intersecting area of the wiring 2594 and the one of the electrodes2592 is preferably as small as possible. Such a structure allows areduction in the area of a region where the electrodes are not provided,reducing unevenness in transmittance. As a result, unevenness in theluminance of light from the touch sensor 2595 can be reduced.

Note that the shapes of the electrodes 2591 and the electrodes 2592 arenot limited to the above-mentioned shapes and can be any of a variety ofshapes. For example, the plurality of electrodes 2591 may be provided sothat space between the electrodes 2591 are reduced as much as possible,and a plurality of electrodes 2592 may be provided with an insulatinglayer sandwiched between the electrodes 2591 and the electrodes 2592. Inthat case, between two adjacent electrodes 2592, it is preferable toprovide a dummy electrode which is electrically insulated from theseelectrodes, whereby the area of a region having a differenttransmittance can be reduced.

Next, the touch panel 2000 will be described in detail with reference toFIGS. 12A and 12B. FIG. 12A is a cross-sectional view taken alongdashed-dotted line X1-X2 in FIG. 11A.

The touch sensor 2595 includes the electrodes 2591 and the electrodes2592 provided in a staggered arrangement on the substrate 2590, aninsulating layer 2593 covering the electrodes 2591 and the electrodes2592, and the wiring 2594 that electrically connects the adjacentelectrodes 2591 to each other.

An adhesive layer 2597 is provided below the wiring 2594. The substrate2590 is attached to the substrate 2570 with the adhesive layer 2597 sothat the touch sensor 2595 overlaps with the display portion 2501.

The electrodes 2591 and the electrodes 2592 are formed using alight-transmitting conductive material. As a light-transmittingconductive material, a conductive oxide such as indium oxide, indium tinoxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium isadded can be used. Note that a film containing graphene may be used aswell. The film including graphene can be formed, for example, byreducing a film containing graphene oxide. As a reducing method, amethod with application of heat or the like can be employed.

For example, the electrodes 2591 and the electrodes 2592 may be formedby depositing a light-transmitting conductive material on the substrate2590 by a sputtering method and then removing an unnecessary portion byany of various patterning techniques such as photolithography.

Examples of a material for the insulating layer 2593 are a resin such asacrylic or epoxy resin, a resin having a siloxane bond, and an inorganicinsulating material such as silicon oxide, silicon oxynitride, oraluminum oxide.

The wiring 2594 is formed in an opening provided in the insulating layer2593, whereby the adjacent electrodes 2591 are electrically connected toeach other. A light-transmitting conductive material can be favorablyused for the wiring 2594 because the aperture ratio of the touch panelcan be increased. Moreover, a material having higher conductivity thanthe electrodes 2591 and 2592 can be favorably used for the wiring 2594because electric resistance can be reduced.

Through the wiring 2594, a pair of electrodes 2591 is electricallyconnected to each other. Between the pair of electrodes 2591, theelectrode 2592 is provided.

One wiring 2598 is electrically connected to any of the electrodes 2591and 2592. Part of the wiring 2598 serves as a terminal. For the wiring2598, a metal material such as aluminum, gold, platinum, silver, nickel,titanium, tungsten, chromium, molybdenum, iron, cobalt, copper, orpalladium or an alloy material containing any of these metal materialscan be used.

Through the connection layer 2599, the wiring 2598 and the FPC 2509(2)are electrically connected to each other. The connection layer 2599 canbe formed using any of various kinds of anisotropic conductive films(ACF), anisotropic conductive pastes (ACP), and the like.

The adhesive layer 2597 has a light-transmitting property. For example,a thermosetting resin or an ultraviolet curable resin can be used;specifically, a resin such as an acrylic-based resin, an urethane-basedresin, an epoxy-based resin, or a siloxane-based resin can be used.

The display portion 2501 includes a plurality of pixels arranged in amatrix. Each of the pixels includes a display element and a pixelcircuit for driving the display element.

For the substrate 2510 and the substrate 2570, for example, a flexiblematerial having a vapor permeability of 10⁻⁵ g/(m²·day) or lower,preferably 10⁻⁶ g/(m²·day) or lower can be favorably used. Note thatmaterials whose thermal expansion coefficients are substantially equalto each other are preferably used for the substrate 2510 and thesubstrate 2570 respectively. For example, the coefficient of linearexpansion of the materials are preferably lower than or equal to1×10⁻³/K, further preferably lower than or equal to 5×10⁻⁵/K, and stillfurther preferably lower than or equal to 1×10⁻⁵/K.

A sealing layer 2560 preferably has a higher refractive index than theair.

The display portion 2501 includes a pixel 2502R. The pixel 2502Rincludes a light-emitting module 2580R.

The pixel 2502R includes a light-emitting element 2550R and a transistor2502 t that can supply electric power to the light-emitting element2550R. Note that the transistor 2502 t functions as part of the pixelcircuit. The light-emitting module 2580R includes the light-emittingelement 2550R and a coloring layer 2567R.

The light-emitting element 2550R includes a lower electrode, an upperelectrode, and an EL layer between the lower electrode and the upperelectrode.

In the case where the sealing layer 2560 is provided on the lightextraction side, the sealing layer 2560 is in contact with thelight-emitting element 2550R and the coloring layer 2567R.

The coloring layer 2567R overlaps with the light-emitting element 2550R.Accordingly, part of light emitted from the light-emitting element 2550Rpasses through the coloring layer 2567R and is emitted to the outside ofthe light-emitting module 2580R as indicated by an arrow in FIG. 12A.

The display portion 2501 includes a light-blocking layer 2567BM on thelight extraction side. The light-blocking layer 2567BM is provided so asto surround the coloring layer 2567R.

The display portion 2501 includes an anti-reflective layer 2567 p in aregion overlapping with pixels. As the anti-reflective layer 2567 p, acircular polarizing plate can be used, for example.

An insulating layer 2521 is provided in the display portion 2501. Theinsulating layer 2521 covers the transistor 2502 t. With the insulatinglayer 2521, unevenness caused by the pixel circuit is planarized. Theinsulating layer 2521 may serve also as a layer for preventing diffusionof impurities. This can prevent a reduction in the reliability of thetransistor 2502 t or the like due to diffusion of impurities.

The light-emitting element 2550R is formed above the insulating layer2521. A partition 2528 is provided so as to cover end portions of thelower electrode in the light-emitting element 2550R. Note that a spacerfor controlling the distance between the substrate 2510 and thesubstrate 2570 may be provided over the partition 2528.

A scan line driver circuit 2503 g(1) includes a transistor 2503 t and acapacitor 2503 c. Note that the driver circuit and the pixel circuitscan be formed in the same process over the same substrate.

Over the substrate 2510, the wirings 2511 through which a signal can besupplied are provided. Over the wirings 2511, the terminal 2519 isprovided. The FPC 2509(1) is electrically connected to the terminal2519. The FPC 2509(1) has a function of supplying signals such as apixel signal and a synchronization signal. Note that a printed wiringboard (PWB) may be attached to the FPC 2509(1).

For the display portion 2501, transistors with a variety of structurescan be used. In the example of FIG. 12A, a bottom-gate transistor isused. In each of the transistor 2502 t and the transistor 2503 tillustrated in FIG. 12A, a semiconductor layer including an oxidesemiconductor can be used for a channel region. Alternatively, in eachof the transistor 2502 t and the transistor 2503 t, a semiconductorlayer including amorphous silicon can be used for a channel region.Further alternatively, in each of the transistor 2502 t and thetransistor 2503 t, a semiconductor layer including polycrystallinesilicon that is obtained by crystallization process such as laserannealing can be used for a channel region.

FIG. 12B illustrates the structure of the display portion 2501 in whicha top-gate transistor is used.

In the case of a top-gate transistor, a semiconductor layer includingpolycrystalline silicon, a single crystal silicon film that istransferred from a single crystal silicon substrate, or the like may beused for a channel region as well as the above semiconductor layers thatcan be used for a bottom-gate transistor.

Next, a touch panel having a different structure from that illustratedin FIGS. 12A and 12B will be described with reference to FIGS. 13A and13B.

FIGS. 13A and 13B are cross-sectional views of a touch panel 2001. Inthe touch panel 2001 illustrated in FIGS. 13A and 13B, the position ofthe touch sensor 2595 relative to the display portion 2501 is differentfrom that in the touch panel 2000 illustrated in FIGS. 12A and 12B.Different structures will be described in detail below, and the abovedescription of the touch panel 2000 can be referred to for the othersimilar structures.

The coloring layer 2567R overlaps with the light-emitting element 2550R.The light-emitting element 2550R illustrated in FIG. 13A emits light tothe side where the transistor 2502 t is provided. Accordingly, part oflight emitted from the light-emitting element 2550R passes through thecoloring layer 2567R and is emitted to the outside of the light-emittingmodule 2580R as indicated by an arrow in FIG. 13A.

The display portion 2501 includes the light-blocking layer 2567BM on thelight extraction side. The light-shielding layer 2567BM is provided soas to surround the coloring layer 2567R.

The touch sensor 2595 is provided on the substrate 2510 side of thedisplay portion 2501 (see FIG. 13A).

The display portion 2501 and the touch sensor 2595 are attached to eachother with the adhesive layer 2597 provided between the substrate 2510and the substrate 2590.

For the display portion 2501, transistors with a variety of structurescan be used. In the example of FIG. 13A, a bottom-gate transistor isused. In the example of FIG. 13B, a top-gate transistor is used.

Then, an example of a driving method of the touch panel will bedescribed with reference to FIGS. 14A and 14B.

FIG. 14A is a block diagram illustrating the structure of a mutualcapacitive touch sensor. FIG. 14A illustrates a pulse voltage outputcircuit 2601 and a current sensing circuit 2602. Note that in theexample of FIG. 14A, six wirings X1-X6 represent electrodes 2621 towhich a pulse voltage is supplied, and six wirings Y1-Y6 representelectrodes 2622 that sense a change in current. FIG. 14A alsoillustrates a capacitor 2603 that is formed in a region where theelectrodes 2621 and 2622 overlap with each other. Note that functionalreplacement between the electrodes 2621 and 2622 is possible.

The pulse voltage output circuit 2601 is a circuit for sequentiallyapplying a pulse voltage to the wirings X1 to X6. By application of apulse voltage to the wirings X1 to X6, an electric field is generatedbetween the electrodes 2621 and 2622 of the capacitor 2603. When theelectric field between the electrodes is shielded, for example, a changeoccurs in the capacitor 2603 (mutual capacitance). The approach orcontact of a sensing target can be sensed by utilizing this change.

The current sensing circuit 2602 is a circuit for detecting changes incurrent flowing through the wirings Y1 to Y6 that are caused by thechange in mutual capacitance in the capacitor 2603. No change in currentvalue is detected in the wirings Y1 to Y6 when there is no approach orcontact of a sensing target, whereas a decrease in current value isdetected when mutual capacitance is decreased owing to the approach orcontact of a sensing target. Note that an integrator circuit or the likeis used for detection of current values.

FIG. 14B is a timing chart showing input and output waveforms in themutual capacitive touch sensor illustrated in FIG. 14A. In FIG. 14B,sensing of a sensing target is performed in all the rows and columns inone frame period. FIG. 14B shows a period when a sensing target is notsensed (not touched) and a period when a sensing target is sensed(touched). Sensed current values of the wirings Y1 to Y6 are shown asthe waveforms of voltage values.

A pulse voltage is sequentially applied to the wirings X1 to X6, and thewaveforms of the wirings Y1 to Y6 change in accordance with the pulsevoltage. When there is no approach or contact of a sensing target, thewaveforms of the wirings Y1 to Y6 change in accordance with changes inthe voltages of the wirings X1 to X6. The current value is decreased atthe point of approach or contact of a sensing target and accordingly thewaveform of the voltage value changes. By detecting a change in mutualcapacitance in this manner, the approach or contact of a sensing targetcan be sensed.

Although FIG. 14A is a passive touch sensor in which only the capacitor2603 is provided at the intersection of wirings as a touch sensor, anactive touch sensor including a transistor and a capacitor may be used.FIG. 15 is a sensor circuit included in an active touch sensor.

The sensor circuit illustrated in FIG. 15 includes the capacitor 2603, atransistor 2611, a transistor 2612, and a transistor 2613.

A signal G2 is input to a gate of the transistor 2613. A voltage VRES isapplied to one of a source and a drain of the transistor 2613, and oneelectrode of the capacitor 2603 and a gate of the transistor 2611 areelectrically connected to the other of the source and the drain of thetransistor 2613. One of a source and a drain of the transistor 2611 iselectrically connected to one of a source and a drain of the transistor2612, and a voltage VSS is applied to the other of the source and thedrain of the transistor 2611. A signal G1 is input to a gate of thetransistor 2612, and a wiring ML is electrically connected to the otherof the source and the drain of the transistor 2612. The voltage VSS isapplied to the other electrode of the capacitor 2603.

Next, the operation of the sensor circuit illustrated in FIG. 15 will bedescribed. First, a potential for turning on the transistor 2613 issupplied as the signal G2, and a potential with respect to the voltageVRES is thus applied to the node n connected to the gate of thetransistor 2611. Then, a potential for turning off the transistor 2613is applied as the signal G2, whereby the potential of the node n ismaintained. Then, mutual capacitance of the capacitor 2603 changes owingto the approach or contact of a sensing target such as a finger, andaccordingly the potential of the node n is changed from VRES.

In reading operation, a potential for turning on the transistor 2612 issupplied as the signal G1. A current flowing through the transistor2611, that is, a current flowing through the wiring ML is changed inaccordance with the potential of the node n. By sensing this current,the approach or contact of a sensing target can be sensed.

In each of the transistors 2611, 2612, and 2613, an oxide semiconductorlayer is preferably used as a semiconductor layer in which a channelregion is formed. In particular, such a transistor is preferably used asthe transistor 2613 so that the potential of the node n can be held fora long time and the frequency of operation of resupplying VRES to thenode n (refresh operation) can be reduced.

At least part of this embodiment can be implemented in combination withany of the embodiments described in this specification as appropriate.

Example 1

In this example, results of calculating power consumption oflight-emitting devices performing white display will be described. Inthe light-emitting device of the present invention, light-emittingelements (a yellow light-emitting element: Light-emitting Element 1, ablue light-emitting element: Light-emitting Element 2, and a greenlight-emitting element: Light-emitting Element 3) were used. In thelight-emitting device of a comparative example, light-emitting elements(a yellow light-emitting element: Comparative Light-emitting Element 1,a blue light-emitting element: Comparative Light-emitting Element 2, anda red light-emitting element: Comparative Light-emitting Element 3) wereused.

The reason why Light-emitting Elements 1 to 3 are light-emittingelements that emit yellow light, blue light, and green lightrespectively and Comparative Light-emitting Elements 1 to 3 arelight-emitting elements that emit yellow light, blue light, and redlight respectively is that such light of the colors are needed forobtaining white light having chromaticity at approximately D65 (lighthaving chromaticity coordinates of (x, y)=(0.313, 0.329) on the xychromaticity diagram). Note that red light is not needed for obtainingwhite light in the light-emitting device of this example, and greenlight is not needed for obtaining white light in the light-emittingdevice of the comparative example; therefore, description thereof isomitted.

Structure formulae of organic compounds used in Light-emitting Elements1 to 3 and Comparative Light-emitting Elements 1 to 3 are shown below.

(Methods for Fabricating Light-Emitting Elements 1 to 3 and ComparativeLight-Emitting Elements 1 to 3)

First, an alloy film of silver (Ag), palladium (Pd), and copper (Cu)(the alloy film is hereinafter referred to as APC) was formed over aglass substrate by a sputtering method to form a first electrode(reflective electrode). The thickness of the first electrode was 100 nmand the electrode area was 2 mm×2 mm.

Next, as a transparent conductive film, a film of indium tin oxidecontaining silicon oxide was formed over the first electrode by asputtering method. The thickness of the transparent conductive film forLight-emitting Element 1 was 30 nm, that for Light-emitting Element 2was 80 nm, and that for Light-emitting Element 3 was 30 nm. Thethickness of the transparent conductive film for ComparativeLight-emitting Element 1 was 30 nm, that for Comparative Light-emittingElement 2 was 60 nm, and that for Comparative Light-emitting Element 3was 60 nm.

Then, as pretreatment of evaporation of an organic compound layer, asurface of the substrate provided with the reflective electrode and thetransparent conductive film was washed with water, baking was performedat 200° C. for one hour, and then UV ozone treatment was performed for370 seconds.

After that, the substrate was transferred into a vacuum evaporationapparatus in which the pressure had been reduced to approximately 10⁻⁴Pa, and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate was cooled down for about 30 minutes.

Then, the substrate was fixed to a substrate holder provided in thevacuum evaporation apparatus so that the surface on which thetransparent conductive film was formed faced downward. The pressure inthe vacuum evaporation apparatus was reduced to approximately 10⁻⁴ Pa.After that, on the transparent conductive film,3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn)represented by Structural Formula (i) and molybdenum(VI) oxide weredeposited by co-evaporation using resistance heating, whereby a firsthole-injection layer was formed. The thickness of the firsthole-injection layer for Light-emitting Element 1 was 60 nm, that forLight-emitting Element 2 was 47.5 nm, and that for Light-emittingElement 3 was 40 nm. The thickness of the first hole-injection layer forComparative Light-emitting Element 1 was 55 nm, that for ComparativeLight-emitting Element 2 was 70 nm, and that for ComparativeLight-emitting Element 3 was 45 nm. The weight ratio of PCPPn tomolybdenum oxide was adjusted to 1:0.5.

Next, on the first hole-injection layer, PCPPn was deposited to athickness of 10 nm to form a first hole-transport layer.

As for each of Light-emitting Elements 1 to 3, on the firsthole-transport layer, a first light-emitting layer was formed bydeposition of 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) represented by Structural Formula (ii) andN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03) represented by Structural Formula (iii) toa thickness of 25 nm so that the weight ratio of cgDBCzPA to1,6BnfAPrn-03 was 1:0.05.

As for each of Comparative Light-emitting Elements 1 to 3, on the firsthole-transport layer, a first light-emitting layer was formed bydeposition of cgDBCzPA andN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn) represented by Structural Formula (x) toa thickness of 25 nm so that the weight ratio of cgDBCzPA to1,6mMemFLPAPrn was 1:0.05.

Then, a first electron-transport layer was formed over the firstlight-emitting layer in such a way that cgDBCzPA was deposited to athickness of 5 nm and bathophenanthroline (abbreviation: BPhen)represented by Structural Formula (iv) was deposited to a thickness of15 nm.

After the first electron-transport layer was formed, lithium oxide(Li₂O) was evaporated to a thickness of 0.1 nm. Then, copperphthalocyanine (abbreviation: CuPc) represented by Structural Formula(xi) was evaporated to a thickness or 2 nm After that,4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II) represented by Structural Formula (v) and molybdenum(VI) oxidewere co-evaporated so that the weight ratio of DBT3P-II to molybdenumoxide was 1:0.5. In such a manner, an intermediate layer was formed. Thethickness of the intermediate layer was 12.5 nm.

Next, on the intermediate layer,4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP)represented by Structural Formula (vi) was evaporated to a thickness of20 nm, whereby a second hole-transport layer was formed.

After the second hole-transport layer was formed,2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[0]quinoxaline(abbreviation: 2mDBTBPDBq-II) represented by Structural Formula (vii),N-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF) represented by Structural Formula (viii), andbis{2-[5-methyl-6-(2-methylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]) represented by Structural Formula(ix) were co-evaporated so that the weight ratio of 2mDBTBPDBq-II toPCBBiF and [Ir(mpmppm)₂(acac)] was 0.8:0.2:0.06. In this manner, asecond light-emitting layer was formed. The thickness of the secondlight-emitting layer was 40 nm.

Then, on the second light-emitting layer, 2mDBTBPDBq-II was evaporatedto a thickness of 15 nm. As for each of Light-emitting Elements 1 to 3,BPhen was also evaporated to a thickness of 20 nm. As for each ofComparative Light-emitting Elements 1 to 3, BPhen was also evaporated toa thickness of 15 nm. In this manner, a second electron-transport layerwas formed.

After that, lithium fluoride was evaporated to a thickness of 1 nm toform an electron-injection layer. Then, silver and magnesium wereco-evaporated to a thickness of 15 nm with a volume ratio of 1:0.1(=silver:magnesium). Next, ITO was deposited to a thickness of 70 nm bya sputtering method. In this manner, a second electrode(semi-transmissive and semi-reflective electrode) was formed. Throughthe above steps, Light-emitting Elements 1 to 3 and ComparativeLight-emitting Elements 1 to 3 were fabricated. Note that in all theabove evaporation steps, evaporation was performed by aresistance-heating method.

The element structures of Light-emitting Elements 1 to 3 and ComparativeLight-emitting Elements 1 to 3 are listed below.

TABLE 1 Hole- First First Reflective injection Hole-transport FirstLight-emitting Electron-transport Electrode Layer Layer Layer Layer APCITSO PCPPn:MoOx PCPPn cgDBCzPA:*1 cgDBCzPA BPhen 1:0.5 1:0.05 100 nm *3*4 10 nm 25 nm 5 nm 15 nm Second Hole-transport Second Light-emittingSecond Electron-transport Intermediate Layer Layer Layer Layer Li₂O CuPCDBT3P-II:MoOx BPAFLP 2mDBTBPDBq-II:PCBBiF:[Ir(mpmppm)₂(acac)]2mDBTBPDBq-II BPhen 1:0.5 0.8:0.2:0.06 0.1 nm 2 nm 12.5 nm 20 nm 40 nm15 nm *5 Electron-injection Semi-transmissive and Layer Semi-reflectiveElectrode Color Filter LiF Ag:Mg ITO *2 1:0.1 1 nm 15 nm 70 nm *1Light-emitting Elements 1 to 3: 1,6BnfAPrn-03 Comparative Light-emittingElements 1 to 3: 1,6mMemFLPAPrn *2 Light-emitting Element 1 andComparative Light-emitting Element 1: 0.8 μm Light-emitting Elemenet 2and Comparative Light-emitting Element 2: Blue 0.8 μm Light-emittingElement 3: Green 1.3 μm, Comparative Light-emitting Element 3: Red 2.4μm *3 Light-emitting Element 1: 30 nm, Light-emitting Element 2: 80 nm,Light-emitting Element 3: 30 nm Comparative Light-emitting Element 1: 30nm, Comparative Light-emitting Element 2:60 nm, ComparativeLight-emitting Element 3: 60 nm *4 Light-emitting Element 1: 60 nm,Light-emitting Element 2: 47.5 nm, Light-emitting Element 3: 40 nmComparative Light-emitting Element 1: 55 nm, Comparative Light-emittingElement 2:70 nm, Comparative Light-emitting Element 3: 45 nm *5Light-emitting Elements 1 to 3: 20 nm

Comparative Light-Emitting Elements 1 to 3: 15 nm

Each of Light-emitting Elements 1 to 3 and Comparative Light-emittingElements 1 to 3 was sealed using a glass substrate in a glove boxcontaining a nitrogen atmosphere so as not to be exposed to the air(specifically, a sealing material was applied to surround the element,and at the time of sealing, UV treatment (with 365-nm ultraviolet lightat 6 J/cm²) was performed and heat treatment was performed at 80° C. for1 hour). Then, initial characteristics of these light-emitting elementswere measured. Note that the measurement was carried out at roomtemperature (in an atmosphere kept at 25° C.).

FIG. 16 shows luminance-current density characteristics ofLight-emitting Elements 1 to 3, FIG. 17 shows currentefficiency-luminance characteristics thereof, FIG. 18 showsluminance-voltage characteristics thereof, FIG. 19 shows current-voltagecharacteristics thereof, and FIG. 20 shows chromaticity coordinatesthereof.

FIG. 21 shows luminance-current density characteristics of ComparativeLight-emitting Elements 1 to 3, FIG. 22 shows currentefficiency-luminance characteristics thereof, FIG. 23 showsluminance-voltage characteristics thereof, FIG. 24 shows current-voltagecharacteristics thereof, and FIG. 25 shows chromaticity coordinatesthereof.

As in FIG. 20 and FIG. 25, Light-emitting Element 2 including1,6BnfAPrn-03 has chromaticity coordinates of (x, y)=(0.152, 0.037) ataround 1000 cd/m², and Comparative Light-emitting Element 2 including1,6mMemFLPAPrn has chromaticity coordinates of (x, y)=(0.160, 0.087).This shows that Light-emitting Elements 2 exhibits deeper blue emissionthan Comparative Light-emitting Element 2.

FIG. 26 shows the emission spectrum of 1,6BnfAPrn-03 in a toluenesolution of 1,6BnfAPrn-03. As seen from FIG. 26, the peak wavelength ofthe emission spectrum of 1,6BnfAPrn-03 in the toluene solution was 450nm. The half-width of the emission spectrum was 40 nm. On the otherhand, the peak wavelength of 1,6mMemFLPAPrn in the toluene solution usedfor the comparative light-emitting elements was 461 nm.

Next, power consumption for obtaining white light having chromaticity atapproximately D65 of the light-emitting devices including thelight-emitting elements was calculated. The power consumption of thelight-emitting devices was calculated under the following conditions.

TABLE 2 Panel Size 4.3 (inch) (Aspect Ratio 16:9) Panel Area 51.0 (cm²)Aperture Ratio 35% All White (Effective Luminance) 300 (cd/m²)

Table 3 shows the calculation results of the light-emitting device ofthis example, and Table 4 shows the calculation results of thelight-emitting device of the comparative example.

TABLE 3 Effective Intrinsic Current Current Power Light-emittingLuminance Luminance Efficiency Current Density Amount VoltageConsumption Element Chromaticity x Chromaticity y (cd/m²) (cd/m²) (cd/A)(mA/cm²) (mA) (V) (mW) 1(Yellow) 0.449 0.545 253 2895 142.6 2.0 9.1 5.9253.6 2(Blue) 0.152 0.038 15 175 2.3 7.7 34.4 6.38 219.2 3(Green) 0.3360.653 31 358 38.7 0.9 4.1 5.50 22.7 All White 0.313 0.329 300 — — — 47.5— 295.6

TABLE 4 Comparative Effective Intrinsic Current Current PowerLight-emitting Luminance Luminance Efficiency Current Density AmountVoltage Consumption Element Chromaticity x Chromaticity y (cd/m²)(cd/m²) (cd/A) (mA/cm²) (mA) (V) (mW) 1(Yellow) 0.414 0.582 237 2705126.7 2.1 9.5 5.96 56.8 2(Blue) 0.160 0.088 38 435 5.2 8.4 37.5 7.05264.3 3(Red) 0.656 0.344 25 289 19.1 1.5 6.7 5.82 39.1 All White 0.3130.329 300 — — — 53.7 — 360.2

In the above calculation results, the effective luminance was obtainedfrom the calculation of intrinsic luminance×aperture ratio×¼ (the arearatio of each subpixel (assuming that one pixel includes four subpixelsof red, green, blue, and yellow in the light-emitting devices)); thecurrent amount was obtained from the calculation of currentdensity×panel area×aperture ratio×¼ (the area ratio of each subpixel);and the power consumption of a display portion was obtained from thecalculation of current amount×voltage.

As seen from Table 3 and Table 4, the luminance of blue emission(emission of Light-emitting Element 2) needed for obtaining white lighthaving chromaticity at approximately D65 of the light-emitting device ofthis example was as low as 15 cd/m², whereas the luminance of blueemission (emission of Comparative Light-emitting Element 2) needed forobtaining white light having chromaticity at approximately D65 of thelight-emitting device of the comparative example was 38 cd/m². This isbecause the chromaticity of blue emission was improved by using, as ablue emission material, 1,6BnfAPrn-03 that is such a fluorescentsubstance as is described in Embodiment 1 and Embodiment 2, and thus theeffective luminance of the blue emission needed for white light wasreduced. Accordingly, the power consumption of Light-emitting Element 2needed for obtaining white light was significantly reduced.

The power consumption of Light-emitting Element 3 needed for obtainingwhite light having chromaticity at approximately D65 was as low as 22.7mW, whereas the power consumption of Comparative Light-emitting Element3 needed for obtaining white light having chromaticity at approximatelyD65 was 39.1 mW. This also shows that the power consumption of thelight-emitting device of this example is lower.

The reason for this is as follows: deep blue emission was obtained fromLight-emitting Element 2, and thus the color of emission obtained bysynthesis of the blue emission and yellow emission of Light-emittingElement 1 was changed and the color of third emission needed forobtaining white light having chromaticity at approximately D65 waschanged. In the light-emitting device of this example, green emissionwas needed as the third emission. On the other hand, in thelight-emitting device of the comparative example, red emission wasneeded as the third emission. The proportion of luminance needed for thegreen emission of the light-emitting device of this example forobtaining the white light is higher than that for the red emission ofthe light-emitting device of the comparative example for obtaining thewhite light.

However, the luminosity factor of the green emission is higher than thatof the red emission, and thus the current efficiency of Light-emittingElement 3 that exhibits the green emission is about twice as high asthat of Comparative Light-emitting Element 3 that exhibits the redemission. Therefore, even in the case where the proportion of luminanceof the third emission (emission of Light-emitting Element 3) needed forobtaining the white light in the light-emitting device of this exampleis increased, the power consumption of Light-emitting Element 3 can belower than that of Comparative Light-emitting Element 3.

The effective luminance of Light-emitting Element 2 (blue) and that ofLight-emitting Element 3 (green) needed for obtaining white light havingchromaticity at approximately D65 with a luminance of 300 cd/m² in thelight-emitting element of this example are respectively lower than thatof Comparative Light-emitting Element 2 (blue) and that of ComparativeLight-emitting Element 3 (red) needed for obtaining white light havingchromaticity at approximately D65 with a luminance of 300 cd/m² in thelight-emitting element of the comparative example; however, theshortfall can be compensated for by high luminance of yellow emission ofLight-emitting Element 1. Since the current efficiency of Light-emittingElement 1 that exhibits yellow emission is significantly high, anincrease in power consumption due to the increase in needed luminancecan be canceled by a decrease in the luminance needed for Light-emittingElement 2 and Light-emitting Element 3. Consequently, a reduction inpower consumption of the light-emitting device of this example can beachieved.

As a result, the power consumption of the light-emitting device of thisexample that performs white display except the power consumption ofdriving FETs was 5.8 mW/cm², and that including the power consumption ofthe driving FETs was 14 mW/cm². Since the power consumption of thelight-emitting device of the comparative example that performs whitedisplay except the power consumption of the driving FETs was 7.1 mW/cm²,and that including the power consumption of the driving FETs was 16mW/cm², the power consumption of the light-emitting device of thisexample can be lower than that of the comparative example by about 10%to 20%. Note that the power consumption of the light-emitting deviceswith driving FETs was estimated with a voltage between an anode and acathode (the sum of voltages of portions of the light-emitting elementsand the driving FETs) of 15 V.

Since the blue light-emitting element consumes much higher power thanthe light-emitting elements of the other colors, an effect of areduction in power consumption due to a change in chromaticity isconsiderable. Furthermore, a reduction in power consumption can beachieved owing to a change in balance relating to the emission colorsfor obtaining white light having chromaticity at approximately D65 andthe proportions of the luminances. As a result, the power consumption ofthe light-emitting device of this example which includes such afluorescent substance as is described in Embodiment 1 can be low.

Example 2

In this example, results of calculating power consumption oflight-emitting devices performing white display will be described. Inthe light-emitting device of the present invention, light-emittingelements (a red light-emitting element: Light-emitting Element 4, ayellow light-emitting element: Light-emitting Element 5, a greenlight-emitting element: Light-emitting Element 6, and a bluelight-emitting element: Light-emitting Element 7) are used. In thelight-emitting device of a comparative example, light-emitting elements(a red light-emitting element: Comparative Light-emitting Element 4, agreen light-emitting element: Comparative Light-emitting Element 5, anda blue light-emitting element: Comparative Light-emitting Element 6) areused.

Structure formulae of organic compounds used in Light-emitting Elements4 to 7 and Comparative Light-emitting Elements 4 to 6 are shown below.

(Methods for Fabricating Light-Emitting Elements 4 to 7 and ComparativeLight-Emitting Elements 4 to 6)

First, an alloy film of silver (Ag), palladium (Pd), and copper (Cu)(the alloy film is hereinafter referred to as APC) was formed over aglass substrate by a sputtering method to form a first electrode(reflective electrode). The thickness of the first electrode was 100 nmand the electrode area was 2 mm×2 mm.

Next, as a transparent conductive film, a film of indium tin oxidecontaining silicon oxide was formed over the first electrode by asputtering method. The thickness of the transparent conductive film forLight-emitting Element 4 (red) was 80 nm, that for Light-emittingElement 5 (yellow) was 45 nm, that for Light-emitting Element 6 (green)was 45 nm, and that for Light-emitting Element 7 (blue) was 80 nm. Thethickness of the transparent conductive film for ComparativeLight-emitting Element 4 (red) was 85 nm, that for ComparativeLight-emitting Element 5 (green) was 45 nm, and that for ComparativeLight-emitting Element 6 (blue) was 110 nm.

Then, as pretreatment of evaporation of an organic compound layer, asurface of the substrate provided with the reflective electrode and thetransparent conductive film was washed with water, baking was performedat 200° C. for one hour, and then UV ozone treatment was performed for370 seconds.

After that, the substrate was transferred into a vacuum evaporationapparatus in which the pressure had been reduced to approximately 10⁻⁴Pa, and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate was cooled down for about 30 minutes.

Then, the substrate was fixed to a substrate holder provided in thevacuum evaporation apparatus so that the surface on which thetransparent conductive film was formed faced downward. The pressure inthe vacuum evaporation apparatus was reduced to approximately 10⁻⁴ Pa.After that, on the transparent conductive film,3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn)represented by Structural Formula (i) and molybdenum(VI) oxide weredeposited by co-evaporation using resistance heating, whereby a firsthole-injection layer was formed. The thickness of the firsthole-injection layer for Light-emitting Element 4 (red) was 30 nm, thatfor Light-emitting Element 5 (yellow) was 40 nm, that for Light-emittingElement 6 (green) was 22.5 nm, and that for Light-emitting Element 7(blue) was 50 nm. The thickness of the first hole-injection layer forComparative Light-emitting Element 4 (red) was 10 nm, that forComparative Light-emitting Element 5 (green) was 10 nm, and that forComparative Light-emitting Element 6 (blue) was 15 nm. The weight ratioof PCPPn to molybdenum oxide was adjusted to 1:0.5.

Next, on the first hole-injection layer, PCPPn was deposited to form afirst hole-transport layer. The thickness of the first hole-transportlayer for each of Light-emitting Elements 4 to 7 was 10 nm, and thethickness of the first hole-transport layer for each of ComparativeLight-emitting Elements 4 to 6 was 15 nm.

On the first hole-transport layer, a first light-emitting layer wasformed by deposition of7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) represented by Structural Formula (ii) andN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03) represented by Structural Formula (iii) toa thickness of 25 nm so that the weight ratio of cgDBCzPA to1,6BnfAPrn-03 was 1:0.05.

Then, a first electron-transport layer was formed over the firstlight-emitting layer in such a way that cgDBCzPA was deposited to athickness of 5 nm and bathophenanthroline (abbreviation: BPhen)represented by Structural Formula (iv) was deposited to a thickness of15 nm.

After the first electron-transport layer was formed, lithium oxide(Li₂O) was evaporated to a thickness of 0.1 nm. Then, copperphthalocyanine (abbreviation: CuPc) represented by Structural Formula(xi) was evaporated to a thickness or 2 nm. After that,4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II) represented by Structural Formula (v) and molybdenum oxidewere co-evaporated so that the weight ratio of DBT3P-II to molybdenumoxide was 1:0.5. In such a manner, an intermediate layer was formed. Thethickness of the intermediate layer was 12.5 nm.

Next, on the intermediate layer,4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP)represented by Structural Formula (vi) was evaporated to a thickness of20 nm, whereby a second hole-transport layer was formed.

As for each of Light-emitting Elements 4 to 7, after the secondhole-transport layer was formed,2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[0]quinoxaline(abbreviation: 2mDBTBPDBq-II) represented by Structural Formula (vii),N-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF) represented by Structural Formula (viii), andbis{2-[5-methyl-6-(2-methylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]) represented by Structural Formula(ix) were co-evaporated so that the weight ratio of 2mDBTBPDBq-II toPCBBiF and [Ir(mpmppm)₂(acac)] was 0.8:0.2:0.06. In this manner, asecond light-emitting layer was formed. The thickness of the secondlight-emitting layer was 40 nm.

As for each of Comparative Light-emitting Elements 4 to 6, after thesecond hole-transport layer was formed, 2mDBTBPDBq-II, PCBBiF, andbis[2-(6-tert-butyl-4-pyrimidinyl-κN3)phenyl-κC](2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]) represented by Structural Formula(xii) were co-evaporated to a thickness of 20 nm. After that,2mDBTBPDBq-II andbis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,8-dimethyl-4,6-nonanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmp)₂(divm)]) were co-evaporated to athickness of 20 nm so that the weight ratio of 2mDBTBPDBq-II to[Ir(dmdppr-dmp)₂(divm)] was 1:0.06. In this manner, a secondlight-emitting layer was formed.

As for each of Light-emitting Elements 4 to 7, on the secondlight-emitting layer, 2mDBTBPDBq-II was evaporated to a thickness of 15nm. As for each of Comparative Light-emitting Elements 4 to 6, on thesecond light-emitting layer, 2mDBTBPDBq-II was evaporated to a thicknessof 30 nm. As for each of Light-emitting Elements 4 to 7, on2mDBTBPDBq-II, BPhen was also evaporated to a thickness of 20 nm. As foreach of Comparative Light-emitting Elements 4 to 6, on 2mDBTBPDBq-II,BPhen was also evaporated to a thickness of 15 nm. In this manner, asecond electron-transport layer was formed.

After that, lithium fluoride was evaporated to a thickness of 1 nm toform an electron-injection layer. Then, silver and magnesium wereco-evaporated to a thickness of 15 nm with a volume ratio of 1:0.1(=silver:magnesium). Next, ITO was deposited to a thickness of 70 nm bya sputtering method. In this manner, a second electrode(semi-transmissive and semi-reflective electrode) was formed. Throughthe above steps, Light-emitting Elements 4 to 7 and ComparativeLight-emitting Elements 4 to 6 were fabricated. Note that in all theabove evaporation steps, evaporation was performed by aresistance-heating method.

The element structures of Light-emitting Elements 4 to 7 and ComparativeLight-emitting Elements 4 to 6 are listed below.

TABLE 5 Hole- First Reflective injection Hole-transport FirstLight-emitting First Electron-transport Electrode Layer Layer LayerLayer APC ITSO PCPPn:MoOx PCPPn cgDBCzPA:1,6BnfAPrn-03 cgDBCzPA BPhen1:0.5 1:0.05 100 nm *10 *11 *12 25 nm 5 nm 15 nm Second Hole-transportSecond Light-emitting Second Electron-transport Intermediate Layer LayerLayer Layer Li₂O CuPC DBT3P-II:MoOx BPAFLP *13 2mDBTBPDBq-II BPhen 1:0.50.1 nm 2 nm 12.5 nm 20 nm *14 *15 Electron-injection Semi-transmissiveand Layer Semi-reflective Electrode Color Filter LiF Ag:Mg ITO *16 1:0.11 nm 15 nm 70 nm *10 Light-emitting Element 4: 80 nm, Light-emittingElement 5: 45 nm, Light-emitting Element 6: 45 nm, Light-emittingElement 7: 80 nm Comparative Light-emitting Element 4: 85 nm,Comparative Light-emitting Element 5:45 nm, Comparative Light-emittingElement 6: 110 nm *11 Light-emitting Element 4: 30 nm, Light-emittingElement 5: 40 nm, Light-emitting Element 6: 22.5 nm, Light-emittingElement 7: 50 nm Comparative Light-emitting Element 4: 10 nm,Comparative Light-emitting Element 5:10 nm, Comparative Light-emittingElement 6: 15 nm *12 Light-emitting Elements 4 to 7: 10 nm, ComparativeLight-emitting Elements 4 to 6: 15 nm *13 Light-emitting Elements 4 to 72mDBTBPDBq-II:PCBBiF:[Ir(mpmppm)₂(acac)] = 0.8:0.2:0.06, 40 nmComparative Light-emitting Elements 4 to 62mDBTBPDBq-II:PCBBiF:[Ir(tBuppm)₂(acac)] = 0.7:0.3:0.06, 20 nm+2mDBTBPDBq-II:[Ir(dmdppr-dmp)₂(divm)] = 1:0.06, 20 nm *14Light-emitting Elements 4 to 7: 15 nm, Comparative Light-emittingElements 4 to 6: 30 nm *15 Light-emitting Elements 4 to 7: 20 nm,Comparative Light-emitting Elements 4 to 6: 15 nm *16 Light-emittingElement 4 and Comparative Light-emitting Element 4: Red 2.4 μmLight-emitting Element 5: Yellow 0.8 μm Light-emitting Element 6 andComparative Light-emitting Element 5: Green 1.3 μm Light-emittingElement 7 and Comparative Light-emitting Element 6: Blue 0.8 μm

Each of Light-emitting Elements 4 to 7 and Comparative Light-emittingElements 4 to 6 was sealed using a glass substrate in a glove boxcontaining a nitrogen atmosphere so as not to be exposed to the air(specifically, a sealing material was applied to surround the element,and at the time of sealing, UV treatment (with 365-nm ultraviolet lightat 6 J/cm²) was performed and heat treatment was performed at 80° C. for1 hour). Then, initial characteristics of these light-emitting elementswere measured. Note that the measurement was carried out at roomtemperature (in an atmosphere kept at 25° C.).

FIG. 28 shows luminance-current density characteristics ofLight-emitting Elements 4 to 7, FIG. 29 shows currentefficiency-luminance characteristics thereof, FIG. 30 showsluminance-voltage characteristics thereof, FIG. 31 shows current-voltagecharacteristics thereof, and FIG. 32 shows chromaticity coordinatesthereof.

FIG. 33 shows luminance-current density characteristics of ComparativeLight-emitting Elements 4 to 6, FIG. 34 shows currentefficiency-luminance characteristics thereof, FIG. 35 showsluminance-voltage characteristics thereof, and FIG. 36 showscurrent-voltage characteristics thereof.

Next, power consumption for obtaining white light having chromaticity atapproximately D65 of the light-emitting devices including thelight-emitting elements was calculated. The power consumption of thelight-emitting devices was calculated under the following conditions.

TABLE 6 Panel Size 4.3 (inch) (Aspect Ratio 16:9) Panel Area 51.0 (cm²)Aperture Ratio 35% All White (Effective Luminance) 300 (cd/m²)

Table 7 shows the calculation results of the light-emitting device ofthis example, and Table 8 shows the calculation results of thelight-emitting device of the comparative example.

TABLE 7 Current Current Power Light- Volt- Density CIE Lumi- Effi- Con-emitting age (mA/ Chromaticity nance ciency sumption Element (V) cm²)(x, y) (cd/m²) (cd/A) (mW) 4 (Red) — — (0.67, 0.33) — 22.1 0 5 (Yellow)5.9 2.2 (0.44, 0.55) 2956 137 57.2 6 (Green) 5.3 0.23 (0.33, 0.66) 13961.1 5.3 7 (Blue) 6.4 7.2 (0.17, 0.07) 334 4.66 203.7

TABLE 8 Compar- ative Current Intrinsic Current Power Light- Volt-Density CIE Lumi- Effi- Con- emitting age (mA/ Chromaticity nance ciencysumption Element (V) cm²) (x, y) (cd/m²) (cd/A) (mW) 4 (Red) 6.0 2.1(0.67, 0.33) 572 27.8 73.7 5 (Green) 6.3 2.7 (0.29, 0.70) 1792 67.2 99.26 (Blue) 6.6 5.6 (0.16, 0.06) 208 3.72 221.1

In the above calculation results, the effective luminance was obtainedfrom the calculation of intrinsic luminance×aperture ratio×¼ (the arearatio of each subpixel (assuming that one pixel includes four subpixelsof red, green, blue, and yellow in the light-emitting devices)); thecurrent amount was obtained from the calculation of currentdensity×panel area×aperture ratio×¼ (the area ratio of each subpixel);and the power consumption of a display portion was obtained from thecalculation of current amount×voltage.

As seen from Table 7 and Table 8, the power consumption for obtainingwhite light of the light-emitting device of this example was 266 mW, andthat of the light-emitting device of the comparative example was 394 mW;thus, the light-emitting device of this example consumes lower powerthan that of the comparative example. In the light-emitting device ofthe comparative example, both Comparative Light-emitting Element 4 (red)and Comparative Light-emitting Element 5 (green) need intrinsicluminance to account for certain proportions for emitting white light.On the other hand, in the light-emitting device of this example,Light-emitting Element 4 (red) emits no light and the emission luminanceof Light-emitting Element 6 (green) is as low as 139 cd/m² for emittingwhite light; thus, they do not substantially affect the powerconsumption. That is, in the light-emitting device of this example, onlyLight-emitting Element 7 (blue) and Light-emitting Element 5 (yellow)emit light substantially for exhibiting white emission. Since thecurrent efficiency of Light-emitting Element 5 (yellow) is as high as137 cd/A, the power consumption of the light-emitting device of thisexample was significantly lower than that of the light-emitting deviceof the comparative example although the power consumption of the bluelight-emitting elements of the light-emitting devices of this exampleand the comparative example are substantially the same.

Example 3

The estimated results of luminance degradation in the case where alight-emitting device of one embodiment of the present inventionperforms white display having chromaticity at approximately D65 with aluminance of 300 cd/m² are shown. In this example, driving tests onLight-emitting Element 8 (blue) and Light-emitting Element 9 (yellow)which have the same structure as a light-emitting element in thelight-emitting device of one embodiment of the present invention werecarried out under the condition where the current density was constant.The initial luminance of Light-emitting Element 8 was set to 300 cd/m²,and that of Light-emitting Element 9 was set to 3000 cd/m². These valueswere close to luminance values needed for performing white displayhaving chromaticity at approximately D65 in the light-emitting device ofone embodiment of the present invention with the following conditions.The reason why the driving tests were carried out on the assumption thatwhite display was performed is that light emission needs to becontinuously performed for white display and thus the elements aredegraded the most quickly in performing white display.

TABLE 9 Panel Size 4.3 (inch) (Aspect Ratio 16:9) Panel Area 51.0 (cm²)Aperture Ratio 35% All White (Effective Luminance) 300 (cd/m²)

Note that the driving test was not carried out on a red light-emittingelement or a green light-emitting element because light is extractedfrom a yellow light-emitting layer and thus they probably showdegradation behaviors similar to those of a yellow light-emittingelement and because the luminance needed for the red light-emittingelement and the green light-emitting element in performing white displayhaving chromaticity at approximately D65 is low as described in Example2 and thus they do not affect reliability.

Structural formulae of organic compounds used in Light-emitting Elements8 and 9 are shown below.

(Methods for Fabricating Light-Emitting Elements 8 and 9)

First, an alloy film of silver (Ag), palladium (Pd), and copper (Cu)(the alloy film is hereinafter referred to as APC) was formed over aglass substrate by a sputtering method to form a first electrode(reflective electrode). The thickness of the first electrode was 100 nmand the electrode area was 2 mm×2 mm.

Next, as a transparent conductive film, a film of indium tin oxidecontaining silicon oxide was formed over the first electrode by asputtering method. The thickness of the transparent conductive film forLight-emitting Element 8 (blue) was 85 nm, and that for Light-emittingElement 9 (yellow) was 65 nm.

Then, as pretreatment of evaporation of an organic compound layer, asurface of the substrate provided with the reflective electrode and thetransparent conductive film was washed with water, baking was performedat 200° C. for one hour, and then UV ozone treatment was performed for370 seconds.

After that, the substrate was transferred into a vacuum evaporationapparatus in which the pressure had been reduced to approximately 10⁻⁴Pa, and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate was cooled down for about 30 minutes.

Then, the substrate was fixed to a substrate holder provided in thevacuum evaporation apparatus such that the surface on which thetransparent conductive film was formed faced downward. After that, onthe transparent conductive film,9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA) represented by Structural Formula (xiv) and molybdenum(VI) oxidewere deposited by co-evaporation using resistance heating, whereby afirst hole-injection layer was formed. The thickness of the firsthole-injection layer for Light-emitting Element 8 (blue) was 40 nm, andthat for Light-emitting Element 9 (yellow) was 45 nm. The weight ratioof PCzPA to molybdenum oxide was adjusted to 1:0.5.

Next, on the first hole-injection layer, PCzPA was deposited to form afirst hole-transport layer. The thickness of the first hole-transportlayer was 20 nm.

On the first hole-transport layer, a first light-emitting layer wasformed by deposition of7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) represented by Structural Formula (ii) andN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03) represented by Structural Formula (iii) toa thickness of 25 nm such that the weight ratio of cgDBCzPA to1,6BnfAPrn-03 was 1:0.03.

Then, a first electron-transport layer was formed over the firstlight-emitting layer in such a way that cgDBCzPA was deposited to athickness of 10 nm and bathophenanthroline (abbreviation: BPhen)represented by Structural Formula (vi) was deposited to a thickness of10 nm.

After the first electron-transport layer was formed, lithium oxide(Li₂O) was evaporated to a thickness of 0.1 nm. Then, copperphthalocyanine (abbreviation: CuPc) represented by Structural Formula(xi) was evaporated to a thickness of 2 nm. After that, PCzPA andmolybdenum oxide were co-evaporated such that the weight ratio of PCzPAto molybdenum oxide was 1:0.5. In such a manner, an intermediate layerwas formed. The thickness of the intermediate layer was 12.5 nm.

Next, on the intermediate layer, PCzPA was evaporated to a thickness of20 nm, whereby a second hole-transport layer was formed.

After the second hole-transport layer was formed,2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II) represented by Structural Formula (vii),N-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF) represented by Structural Formula (viii), andbis{2-[5-methyl-6-(2-methylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]) represented by Structural Formula(ix) were co-evaporated such that the weight ratio of 2mDBTBPDBq-II toPCBBiF and [Ir(mpmppm)₂(acac)] was 0.8:0.2:0.06. In this manner, asecond light-emitting layer was formed. The thickness of the secondlight-emitting layer was 40 nm.

On the second light-emitting layer, 2mDBTBPDBq-II was evaporated to athickness of 15 nm. On 2mDBTBPDBq-II, BPhen was evaporated to athickness of 20 nm. In this manner, a second electron-transport layerwas formed.

After that, lithium fluoride was evaporated to a thickness of 1 nm toform an electron-injection layer. Then, silver and magnesium wereco-evaporated to a thickness of 15 nm with a volume ratio of 1:0.1(=silver:magnesium). Next, ITO was deposited to a thickness of 70 nm bya sputtering method. In this manner, a second electrode(semi-transmissive and semi-reflective electrode) was formed. Throughthe above steps, Light-emitting Element 8 (blue) and Light-emittingElement 9 (yellow) were fabricated. Note that in all the aboveevaporation steps, evaporation was performed by a resistance-heatingmethod.

The element structures of Light-emitting Elements 8 and 9 are listedbelow.

TABLE 10 Hole- First Reflective injection Hole-transport FirstLight-emitting First Electron-transport Electrode Layer Layer LayerLayer APC ITSO PCzPA:MoOx PCzPA cgDBCzPA:1,6BnfAPrn-03 cgDBCzPA BPhen1:0.5 1:0.03 100 nm *19 *20 20 nm 25 nm 10 nm 10 nm SecondHole-transport Second Light-emitting Second Electron-transportIntermediate Layer Layer Layer Layer Li₂O CuPC PCzPA:MoOx PCzPA2mDBTBPDBq-II:PCBBiF:[Ir(mpmppm)₂(acac)] 2mDBTBPDBq-II BPhen 1:0.50.8:0.2:0.06 0.1 nm 2 nm 12.5 nm 20 nm 40 nm 15 nm 20 nmElectron-injection Semi-transmissive and Layer Semi-reflective ElectrodeColor Filter LiF Ag:Mg ITO *21 1:0.1 1 nm 15 nm 70 nm *19 Light-emittingElement 8: 85 nm, Light-emitting Element 9: 65 nm *20 Light-emittingElement 8: 40 nm, Light-emitting Element 9: 45 nm *21 Light-emittingElement 8: Blue 0.8 μm, Light-emitting Element9: Yellow 0.8 μm

Each of Light-emitting Element 8 (blue) and Light-emitting Element 9(yellow) was sealed using a glass substrate in a glove box containing anitrogen atmosphere so as not to be exposed to the air (specifically, asealing material was applied to surround the element, and at the time ofsealing, UV treatment (with 365-nm ultraviolet light at 6 J/cm²) wasperformed and heat treatment was performed at 80° C. for 1 hour). Then,initial characteristics of these light-emitting elements were measured.Note that the measurement was carried out at room temperature (in anatmosphere kept at 25° C.). As for Light-emitting Element 8, themeasurement was carried out on light through a blue color filter. As forLight-emitting Element 9, the measurement was carried out on lightthrough a yellow color filter.

FIG. 39 shows luminance-current density characteristics ofLight-emitting Element 8 (blue) and Light-emitting Element 9 (yellow),FIG. 40 shows current efficiency-luminance characteristics thereof, FIG.41 shows luminance-voltage characteristics thereof, FIG. 42 showscurrent-voltage characteristics thereof, and FIG. 43 shows emissionspectra thereof. As shown in these graphs, Light-emitting Element 8 andLight-emitting Element 9 have favorable characteristics.

Next, driving tests on Light-emitting Element 8 (blue) andLight-emitting Element 9 (yellow) were carried out under the conditionswhere the initial luminance of Light-emitting Element 8 was 300 cd/m²,the initial luminance of Light-emitting Element 9 was 3000 cd/m², andthe current density was constant. FIG. 44 shows a change in luminanceover driving time with an initial luminance taken as 100%.

As shown in FIG. 44, it took approximately 2300 hours for the luminanceof Light-emitting Element 8 to decrease to 90% of the initial luminance,and it took approximately 6000 hours for the luminance of Light-emittingElement 9 to decrease to 90% of the initial luminance. These resultsindicate that the light-emitting device of one embodiment of the presentinvention consumes significantly low power, has a little luminancedegradation, and has reliability high enough for practical use.

Example 4

In this example, a 254-ppi light-emitting device using a color filtermethod was fabricated actually. FIG. 37 is a photograph of thefabricated light-emitting device. In each pixel, red, yellow, green, andblue subpixels each having a size of 50 μm square are arranged in a 2×2matrix. FIG. 38 shows a comparison between the power consumption at thetime of displaying a still image in the light-emitting device of thisexample and that in the light-emitting device of a comparative exampleusing a white-color filter method in which red, green, and bluesubpixels are used. The power consumption of panel portions displayingstill images was calculated at a peak luminance of 300 cd/m².

It is obvious from FIG. 38 that the power consumption of thelight-emitting device of this example is lower than that of thelight-emitting device of the comparative example. In particular, areduction in power consumption of the present invention is considerableat the time of displaying an image in which a white display regionoccupies a large area. The power consumption at the time of displayingthe image in which the white display region occupies a large area is thehighest; the higher the proportion of a black display region is, thelower the power consumption per unit area becomes in each panel. This isbecause an OLED emits no light at the time of displaying black, whereasa backlight needs to be kept on in a liquid crystal display.

Reference Example

In this reference example, a method for synthesizingN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03), an organic compound used in this example,is described. Note that a structure of 1,6BnfAPrn-03 is shown below.

Step 1: Synthesis of 6-iodobenzo[b]naphtho[1,2-d]furan

Into a 500 mL three-neck flask were put 8.5 g (39 mmol) ofbenzo[b]naphtho[1,2-d]furan, and the air in the flask was replaced withnitrogen. Then, 195 mL of tetrahydrofuran was added thereto. Thissolution was cooled to −75° C. Then, 25 mL (40 mmol) of n-butyllithium(a 1.59 mol/L n-hexane solution) was dropped into this solution. Afterthe drop, the resulting solution was stirred at room temperature for 1hour.

After a predetermined period of time, the resulting solution was cooledto −75° C. Then, a solution in which 10 g (40 mmol) of iodine had beendissolved in 40 mL of THF was dropped into this solution. After thedrop, the resulting solution was stirred for 17 hours while thetemperature of the solution was returned to room temperature. After apredetermined period of time, an aqueous solution of sodium thiosulfatewas added to the mixture, and the resulting mixture was stirred for 1hour. Then, an organic layer of the mixture was washed with water anddried with magnesium sulfate. After the drying, the mixture wasgravity-filtered to give a solution. The resulting solution wassuction-filtered through Celite (Catalog No. 531-16855 produced by WakoPure Chemical Industries, Ltd.) and Florisil (Catalog No. 540-00135produced by Wako Pure Chemical Industries, Ltd.) to give a filtrate. Theresulting filtrate was concentrated to give a solid. The resulting solidwas recrystallized from toluene to give 6.0 g (18 mmol) of white powderof the target substance in 45% yield. A synthesis scheme of Step 1 isshown below.

Step 2: Synthesis of 6-phenylbenzo[b]naphtho[1,2-d]furan

Into a 200 mL three-neck flask were put 6.0 g (18 mmol) of6-iodobenzo[b]naphtho[1,2-d]furan, 2.4 g (19 mmol) of phenylboronicacid, 70 mL of toluene, 20 mL of ethanol, and 22 mL of an aqueoussolution of potassium carbonate (2.0 mol/L). This mixture was degassedby being stirred while the pressure was reduced. After the degassing,the air in the flask was replaced with nitrogen, and then 480 mg (0.42mmol) of tetrakis(triphenylphosphine)palladium(0) was added to themixture. The resulting mixture was stirred at 90° C. under a nitrogenstream for 12 hours.

After a predetermined period of time, water was added to the mixture,and an aqueous layer was subjected to extraction with toluene. Theextracted solution and the organic layer were combined, and the mixturewas washed with water and then dried with magnesium sulfate. The mixturewas gravity-filtered to give a filtrate. The resulting filtrate wasconcentrated to give a solid, and the resulting solid was dissolved intoluene. The resulting solution was suction-filtered through Celite(Catalog No. 531-16855 produced by Wako Pure Chemical Industries, Ltd.),Florisil (Catalog No. 540-00135 produced by Wako Pure ChemicalIndustries, Ltd.), and alumina to give a filtrate. The resultingfiltrate was concentrated to give a solid. The resulting solid wasrecrystallized from toluene to give a 4.9 g (17 mmol) of a white solidof the target substance in 93% yield. A synthesis scheme of Step 2 isshown below.

Step 3: Synthesis of 8-iodo-6-phenylbenzo[b]naphtho[1,2,d]furan

Into a 300 mL three-neck flask was put 4.9 g (17 mmol) of6-phenylbenzo[b]naphtho[1,2-d]furan, and the air in the flask wasreplaced with nitrogen. Then, 87 mL of tetrahydrofuran (THF) was addedthereto. The resulting solution was cooled to −75° C. Then, 11 mL (18mmol) of n-butyllithium (a 1.59 mol/L n-hexane solution) was droppedinto the solution. After the drop, the resulting solution was stirred atroom temperature for 1 hour. After a predetermined period of time, theresulting solution was cooled to −75° C. Then, a solution in which 4.6 g(18 mmol) of iodine had been dissolved in 18 mL of THF was dropped intothe resulting solution.

The resulting solution was stirred for 17 hours while the temperature ofthe solution was returned to room temperature. After a predeterminedperiod of time, an aqueous solution of sodium thiosulfate was added tothe mixture, and the resulting mixture was stirred for 1 hour. Then, anorganic layer of the mixture was washed with water and dried withmagnesium sulfate. The mixture was gravity-filtered to give a filtrate.The resulting filtrate was suction-filtered through Celite (Catalog No.531-16855 produced by Wako Pure Chemical Industries, Ltd.), Florisil(Catalog No. 540-00135 produced by Wako Pure Chemical Industries, Ltd.),and alumina to give a filtrate. The resulting filtrate was concentratedto give a solid. The resulting solid was recrystallized from toluene togive 3.7 g (8.8 mmol) of a target white solid in 53% yield. A synthesisscheme of Step 3 is shown below.

Step 4: Synthesis of 1,6BnfAPrn-03

Into a 100 mL three-neck flask were put 0.71 g (2.0 mmol) of1,6-dibromopyrene, 1.0 g (10.4 mmol) of sodium-tert-butoxide, 10 mL oftoluene, 0.36 mL (4.0 mmol) of aniline, and 0.3 mL oftri(tert-butyl)phosphine (a 10 wt % hexane solution), and the air in theflask was replaced with nitrogen. To this mixture was added 50 mg (85μmol) of bis(dibenzylideneacetone)palladium(0), and the resultingmixture was stirred at 80° C. for 2 hours.

After a predetermined period of time, to the resulting mixture wereadded 1.7 g (4.0 mmol) of 8-iodo-6-phenylbenzo[b]naphtho[1,2,d]furan,180 mg (0.44 mmol) of 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl(abbreviation: S-Phos), and 50 mg (85 μmol) ofbis(dibenzylideneacetone)palladium(0), and the resulting mixture wasstirred at 100° C. for 15 hours. After a predetermined period of time,the resulting mixture was filtered through Celite (Catalog No. 531-16855produced by Wako Pure Chemical Industries, Ltd.) to give a filtrate. Theresulting filtrate was concentrated to give a solid. The resulting solidwas washed with ethanol and recrystallized from toluene to give 1.38 g(1.4 mmol) of a yellow solid of the target substance in 71% yield.

By a train sublimation method, 1.37 mg (1.4 mmol) of the resultingyellow solid was purified by sublimation. The purification bysublimation was conducted by heating the yellow solid at 370° C. at anargon flow rate of 10 mL/min under a pressure of under a pressure of 2.3Pa. As a result of the purification by sublimation, 0.68 g (0.70 mmol)of the yellow solid was recovered at a collection rate of 50%. Asynthesis scheme of Step 4 is shown below.

Analysis results by nuclear magnetic resonance (¹H-NMR) spectroscopy ofthe yellow solid obtained in Step 4 are described below. The resultsrevealed that 1,6BnfAPrn-03 was obtained.

¹H NMR (dichloromethane-d2, 500 MHz): δ=6.88 (t, J=7.7 Hz, 4H),7.03-7.06 (m, 6H), 7.11 (t, J=7.5 Hz, 2H), 7.13 (d, J=8.0 Hz, 2H),7.28-7.32 (m, 8H), 7.37 (t, J=8.0 Hz, 2H), 7.59 (t, J=7.2 Hz, 2H), 7.75(t, J=7.7 Hz, 2H), 7.84 (d, J=9.0 Hz, 2H), 7.88 (d, J=8.0 Hz, 2H), 8.01(s, 2H), 8.07 (d, J=8.0 Hz, 4H), 8.14 (d, J=9.0 Hz, 2H), 8.21 (d, J=8.0Hz, 2H), 8.69 (d, J=8.5 Hz, 2H).

REFERENCE NUMERALS

101: first electrode, 102: second electrode, 103 a: EL layer, 103 b: ELlayer, 104 a: hole-injection layer, 104 b: hole-injection layer, 105 a:hole-transport layer, 105 b: hole-transport layer, 106: light-emittinglayer, 106 a: light-emitting layer, 106 b: light-emitting layer, 107 a:electron-transport layer, 107 b: electron-transport layer, 108 a:electron-injection layer, 108 b: electron-injection layer, 109:charge-generation layer, 113: first light-emitting layer, 114: secondlight-emitting layer, 121: guest material (fluorescent material), 122:host material, 131: guest material (phosphorescent material), 132: firstorganic compound, 133: second organic compound, 134: exciplex, 501:substrate, 502: FET, 503: first electrode, 504: partition, 505: ELlayer, 506R: light-emitting region, 506G: light-emitting region, 506B:light-emitting region, 506W: light-emitting region, 506Y: light-emittingregion, 507R: light-emitting element, 507G: light-emitting element,507B: light-emitting element, 507W: light-emitting element, 507Y:light-emitting element, 508R: coloring layer, 508G: coloring layer,508B: coloring layer, 508Y: coloring layer, 509: black layer (blackmatrix), 510: second electrode, 511: sealing substrate, 601: elementsubstrate, 602: pixel portion, 603: driver circuit portion (source linedriver circuit), 604 a: driver circuit portion (gate line drivercircuit), 604 b: driver circuit portion (gate line driver circuit), 605:sealant, 606: sealing substrate, 607: wiring, 608: FPC (flexible printedcircuit), 609: FET, 610: FET, 611: switching FET, 612: current controlFET, 613: first electrode (anode), 614: insulator, 615: EL layer, 616:second electrode (cathode), 617: light-emitting element, 618: space,1100: substrate, 1102B: first electrode, 1102G: first electrode, 1102Y:first electrode, 1102R: first electrode, 1103 d: blue light-emittinglayer, 1103 e: hole-injection layer and hole-transport layer, 1103 f:yellow light-emitting layer, 1103 h: electron-transport layer andelectron-injection layer, 1104: second electrode, 1105: black matrix,1106B: color filter, 1106G: color filter, 1106Y: color filter, 1106R:color filter, 1101: sealing substrate, 2000: touch panel, 2001: touchpanel, 2501: display portion, 2502R: pixel, 2502 t: transistor, 2503 c:capacitor, 2503 g: scan line driver circuit, 2503 t: transistor, 2509:FPC, 2510: substrate, 2511: wiring, 2519: terminal, 2521: insulatinglayer, 2528: partition, 2550R: light-emitting element, 2560: sealinglayer, 2567BM: light-blocking layer, 2567 p: anti-reflective layer,2567R: coloring layer, 2570: substrate, 2580R: light-emitting module,2590: substrate, 2591: electrode, 2592: electrode, 2593: insulatinglayer, 2594: wiring, 2595: touch sensor, 2597: adhesive layer, 2598:wiring, 2599: connection layer, 2601: pulse voltage output circuit,2602: current sensing circuit, 2603: capacitor, 2611: transistor, 2612:transistor, 2613: transistor, 2621: electrode, 2622: electrode, 7100:television device, 7101: housing, 7103: display portion, 7105: stand,7107: display portion, 7109: operation key, 7110: remote controller,7201: main body, 7202: housing, 7203: display portion, 7204: keyboard,7205: external connection port, 7206: pointing device, 7302: housing,7304: display panel, 7305: icon indicating time, 7306: another icon,7311: operation button, 7312: operation button, 7313: connectionterminal, 7321: band, 7322: clasp, 7400: mobile phone, 7401: housing,7402: display portion, 7403: operation button, 7404: external connectionportion, 7405: speaker, 7406: microphone, 7407: camera, 7500(1):housing, 7500(2): housing, 7501(1): display portion, 7501(2): displayportion, 7502(1): display portion, 7502(2): display portion, 8001:lighting device, 8002: lighting device, 8003: lighting device, 8004:lighting device, 9310: portable information terminal, 9311: displaypanel, 9312: display region, 9313: hinge, and 9315: housing

This application is based on Japanese Patent Application serial no.2014-162532 filed with Japan Patent Office on Aug. 8, 2014, JapanesePatent Application serial no. 2014-162576 filed with Japan Patent Officeon Aug. 8, 2014, Japanese Patent Application serial no. 2014-241188filed with Japan Patent Office on Nov. 28, 2014, and Japanese PatentApplication serial no. 2015-131156 filed with Japan Patent Office onJun. 30, 2015, the entire contents of which are hereby incorporated byreference.

The invention claimed is:
 1. A light-emitting device comprising: a firstlight-emitting element emitting blue light; a second light-emittingelement emitting green light; a third light-emitting element emittingred light; and a fourth light-emitting element, wherein the firstlight-emitting element, the second light-emitting element, the thirdlight-emitting element, and the fourth light-emitting element comprisethe same EL layer, wherein the EL layer comprises a first EL layercomprising a first light-emitting layer, a second EL layer comprising asecond light-emitting layer, and a charge-generation layer between thefirst EL layer and the second EL layer, wherein the first light-emittinglayer includes a fluorescent substance, wherein the secondlight-emitting layer includes a phosphorescent substance, and whereinthe fluorescent substance is an organic compound in which each of twobenzo[b]naphtho[1,2-d]furanylamine skeletons is independently bonded toa pyrene skeleton.
 2. The light-emitting device according to claim 1,wherein the second light-emitting layer emits yellow phosphorescence. 3.The light-emitting device according to claim 1, wherein a peakwavelength of the blue light is greater than or equal to 400 nm and lessthan or equal to 480 nm, wherein a peak wavelength of the green light isgreater than or equal to 500 nm and less than or equal to 560 nm, andwherein a peak wavelength of the red light is greater than or equal to580 nm and less than or equal to 680 nm.
 4. The light-emitting deviceaccording to claim 1, wherein the fourth light-emitting element emitsyellow light, and wherein a peak wavelength of the yellow light isgreater than or equal to 555 nm and less than or equal to 590 nm.
 5. Thelight-emitting device according to claim 1, wherein the twobenzo[b]naphtho[1,2-d]furanylamine skeletons are respectively bonded tothe 1-position and the 6-position of the pyrene skeleton.
 6. Thelight-emitting device according to claim 1, wherein each of nitrogenatoms in the two benzo[b]naphtho[1,2-d]furanylamine skeletons isindependently bonded to the 6-position or the 8-position of abenzo[b]naphtho[1,2-d]furanyl group.
 7. The light-emitting deviceaccording to claim 1, wherein the organic compound is represented byFormula (G1)

wherein each of Ar¹ and Ar² independently represents a substituted orunsubstituted aryl group having 6 to 13 carbon atoms forming a ring, andwherein each of R¹ to R⁸, R¹⁰ to R¹⁸, and R²⁰ to R²⁸ independentlyrepresents hydrogen, a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, a substituted or unsubstituted alkoxy group having 1to 6 carbon atoms, a cyano group, halogen, a substituted orunsubstituted haloalkyl group having 1 to 6 carbon atoms, or asubstituted or unsubstituted aryl group having 6 to 10 carbon atoms. 8.The light-emitting device according to claim 1, wherein the organiccompound is represented by Formula (G2)

and wherein each of R¹ to R⁸ and R²⁹ to R³⁸ independently representshydrogen, a substituted or unsubstituted alkyl group having 1 to 6carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 6carbon atoms, a cyano group, halogen, a substituted or unsubstitutedhaloalkyl group having 1 to 6 carbon atoms, or a substituted orunsubstituted aryl group having 6 to 10 carbon atoms.
 9. Thelight-emitting device according to claim 1, wherein the organic compoundis represented by Formula (132)


10. An electronic device comprising the light-emitting device accordingto claim
 1. 11. A lighting device comprising the light-emitting deviceaccording to claim
 1. 12. A light-emitting device comprising: a firstlight-emitting element emitting blue light; a second light-emittingelement emitting green light; a third light-emitting element emittingred light; and a fourth light-emitting element emitting yellow light,wherein the first light-emitting element, the second light-emittingelement, the third light-emitting element, and the fourth light-emittingelement comprise the same EL layer, wherein the EL layer comprises afirst EL layer comprising a first light-emitting layer, a second ELlayer comprising a second light-emitting layer, and a charge-generationlayer between the first EL layer and the second EL layer, wherein thefirst light-emitting layer includes a fluorescent substance, wherein thesecond light-emitting layer includes a phosphorescent substance, andwherein a peak wavelength of an emission spectrum of the fluorescentsubstance in a toluene solution of the fluorescent substance is greaterthan or equal to 440 nm and less than or equal to 460 nm.
 13. Thelight-emitting device according to claim 12, wherein the secondlight-emitting layer emits yellow phosphorescence.
 14. Thelight-emitting device according to claim 12, wherein a peak wavelengthof the blue light is greater than or equal to 400 nm and less than orequal to 480 nm, wherein a peak wavelength of the green light is greaterthan or equal to 500 nm and less than or equal to 560 nm, wherein a peakwavelength of the red light is greater than or equal to 580 nm and lessthan or equal to 680 nm, and wherein a peak wavelength of the yellowlight is greater than or equal to 555 nm and less than or equal to 590nm.
 15. The light-emitting device according to claim 12, wherein ahalf-width of the emission spectrum of the fluorescent substance in thetoluene solution is greater than or equal to 20 nm and less than orequal to 50 nm.
 16. The light-emitting device according to claim 12,wherein the first light-emitting element has an x-coordinate greaterthan or equal to 0.13 and less than or equal to 0.17 and a y-coordinategreater than or equal to 0.03 and less than or equal to 0.07 on an xychromaticity diagram.
 17. The light-emitting device according to claim12, wherein the fluorescent substance has an aromatic diamine skeleton.18. The light-emitting device according to claim 12, wherein thefluorescent substance has a pyrenediamine skeleton.
 19. An electronicdevice comprising the light-emitting device according to claim
 12. 20. Alighting device comprising the light-emitting device according to claim12.